Keir Starmer is facing anger over 'extraordinary' claims UK military chiefs are being asked to find billions of pounds in cuts amid the Iran crisis and the threat from Russia.

The heads of the British Army, Royal Navy and Royal Air Force - along with other top brass - are reported to be meeting this week to discuss funding pressures.

They have been asked by Ministry of Defence (MoD) officials to find £3.5billion of 'efficiencies' and other savings this year, according to Sky News.

Sources said the in-year squeeze is because the current defence budget is insufficient to deliver existing plans.

It previously emerged that the MoD is facing a £28billion shortfall between now and 2030, with the Prime Minister said to have been given the dire financial assessment before Christmas.

James Cartlidge, the shadow defence secretary, said it was 'extraordinary' that military chiefs are being asked to find cuts at a time of 'war on two fronts' in the Middle East and Ukraine.

The senior Tory MP pointed to how Labour had spent around £3billion on lifting the two-child benefit cap, adding: 'Politics is always about what you prioritise.'

The row came as Sir Keir faced charges of leaving Britain 'unsafe' with a former Nato chief and Labour minister condemning the PM's 'corrosive complacency'.

Lord Robertson will use a speech later to accuse Sir Keir of failing to act with the country 'under attack', insisting the Iran war should be a 'rude wake-up call'.

In a devastating assessment, he will warn the Government is prioritising 'the ever-expanding welfare budget' over essential security. 

The peer - who helped write Labour's Strategic Defence Review last year - has been backed by military chiefs who said the UK could no longer rely on the 'US cavalry coming to bail us out'. 

They insisted America was right to ridicule the 'big bad' Royal Navy as it was 'too small' to be effective.

Whitehall sources said defence budgets are continually assessed and reprioritised as part of routine management, adding that military chiefs meet regularly to discuss a range of issues.

The MoD has previously announced a Defence Reform and Efficiency Plan to deliver £6billion of savings over five years.

An MoD spokesman said: 'The defence budget is rising to record levels as this Government delivers the biggest boost to defence spending since the Cold War, totalling £270billion this parliament alone.

'Demands on defence are rising, with growing Russian aggression, the crisis in the Middle East and increasing operational requirements.

'We are finalising our Defence Investment Plan that we will publish as soon as possible, putting the best kit and technology into the hands of our forces, rebuilding British industry to make defence an engine for growth and doubling down on our own commitment to Nato.'

In the wake of Lord Robertson's dramatic intervention, Labour grandee Harriet Harman suggested the state pension triple-lock could be means-tested to pay for defence.

The Labour peer told the BBC the triple lock - which sees state pensions increase in line with whichever is highest out of average earnings growth, inflation or 2.5 per cent - is 'one place to be looking' if the Government needs to 'divert some money to defence'.

She said: 'If you're strapped for some cash and need to divert some money to defence, that is one place to be looking.

'And if you've got money going to people who really don't need it and who are extremely well off, then for the same reason they did on the winter fuel allowance I think that they should think about targeting it.' 

It came as Lord Robertson was backed up by another former Labour defence secretary this afternoon. 

Lord John Hutton said that Sir Keir had to regard the issue of military spending as 'the defining moment in his premiership' and 'get a grip' on welfare spending.

Tory leader Kemi Badenoch warned that Sir Keir cannot be 'trusted' to protect Brits, calling for the two-child benefit cap to be restored and funds moved from Net Zero projects. 

The PM told MPs yesterday that the Government is working to finalise the 10-year defence investment plan, but he would not publish proposals that are 'unfunded and not deliverable'.

There is believed to be a funding gap of around £28billion over the next four years in the existing plans, and the Ministry of Defence, Treasury and Downing Street are deadlocked over how to proceed.

The Government has committed to spend 2.5 per cent of GDP on defence by 2027, with a vague 'ambition' to increase that to 3 per cent in the next Parliament.

There is a Nato-agreed target of hitting 3.5 per cent by 2035.

Lord Robertson was defence secretary under Tony Blair from May 1997 until October 1999. He then became a Nato secretary general until 2004. 

He will use a lecture in Salisbury to accuse 'non-military experts in the Treasury' of 'vandalism' in prioritising benefits over defence. 

He will say: 'We cannot defend Britain with an ever-expanding welfare budget.'

Lord Robertson is to warn of a 'corrosive complacency in Britain's political leadership' and say 'lip service is paid to the risks, the threats, the red signals of danger – but even a promised national conversation about defence can't be started'.

With Labour still to publish its long-awaited Defence Investment Plan, the peer will accuse Sir Keir of being unwilling 'to make the necessary investment' – something the Daily Mail has highlighted in its Don't Leave Britain Defenceless campaign. 

He will add: 'We are underprepared. We are underinsured. We are under attack. We are not safe... Britain's national security and safety is in peril.'

Lord Robertson's intervention comes after Vladimir Putin last week sent a Russian warship to escort two of his shadow fleet vessels through the English Channel. 

Sir Keir had previously trumpeted plans to seize sanctioned Russian vessels in British waters.

But the peer is expected to pour scorn on Chancellor Rachel Reeves for using 'a mere 40 words on defence in over an hour' in her Budget speech last year, while last month in her Spring Statement 'she used none'.

Lord Robertson will cite the UK's inability to deploy more than one Royal Navy warship to the Mediterranean within the first fortnight of the Iran war as an example of the 'parlous state' of our current defences.

He will also warn that the UK faces 'crises in logistics, engineering, cyber, ammunition, training and medical resources'.

General Sir Richard Barrons - another author of the SDR - agreed with Lord Robertson that 'there's an enormous gap between where we have to be to keep the country safe in the world we now live in and where we actually are'.

He told BBC Radio 4's Today programme that the future will involve 'a European Nato doing much more and the US doing much less', and the Royal Navy and Royal Air Force were 'too small and too undernourished'.

'The US cavalry is not coming to bail us out now,' he added.

Sir Richard said when US Defence Secretary Pete Hegseth mocked the 'big bad' Royal Navy he 'could not argue'.

'Like many others I hung my head in sorrow. But I couldn't argue with him because although the Royal Navy and the Royal Air Force and the army are, in their bones, outstanding institutions, they are simply too small and too undernourished to deal with the world that we we now live in. And the review says this,' he said. 

At a Defence Committee hearing this morning, chairman Tan Dhesi asked if people are right to 'mock' the funding turmoil.

Veterans Minister Louise Sandher-Jones said: 'I have a huge amount of respect for him and what he has to say. But I would just gently say that we are working very hard to deliver against the recommendations (of his SDR).

'We have already started investment, I can point to various investments we have made on kit and equipment.

'It is great that people are always urging us to go further and faster, I am someone who always wants to go further and faster for sure, but I think we also have to recognise we are putting in a lot of hard work to get this country ready for the challenges we are facing.'

General Sir Gwyn Jenkins, the First Sea Lord, later added: 'This could not be taken more seriously at the moment. I see no sign of complacency among anybody that I work with or provide advice to.' 

Mrs Badenoch has accused Sir Keir of posturing on the world stage over the Middle East war while failing to rearm the nation.

Speaking to Times Radio today Lord Hutton, who was defence secretary under Gordon Brown, said: '[Starmer has] absolutely got to regard this as the defining moment in his premiership, because the threat from Putin isn't going away anytime soon. 

'My worry about what's going on in the Middle East is that Putin will take a lot of comfort from this, the division within Nato, division within the Western powers. 

'He'll know full well the gaps in our defence credibility and he'll be looking to exploit that. 

'We've got a very, very short period of time to start putting this right and sending out the signals to Putin.'

Military and defence industries should be put on a war footing, the former head of the Royal Navy said this afternoon.

Crossbench peer Lord West of Spithead, who served a minister in a previous Labour government, told peers the UK had more work to do to be equipped to deal with threats.

Lord West said: 'I'm delighted the minister has highlighted what is being done now, but I have this feeling we have a long way to catch up. We're nowhere near that position, and we are, I believe in a state where we perhaps ought to put our military and certainly our defence on some sort of war footing, to be able to catch up and be able to do the things we need to do.'

He had earlier said the UK had fallen behind in the ability to track Russian submarines off its coast compared to the Cold War.

In response, defence minister Lord Coaker said: 'The need for this country to move from where it is to a position of war readiness is crucial.

'That is not a Government effort, that is a whole of society effort from this side of the House, from that side of the House, from all parts of the United Kingdom, to deal with the threats that we face our population has to understand the threat that they face, we as a Government have to talk to them, and all of us have to stand up and say 'We will defend our country and the values we stand for'.'