Andy Burnham tried to quell a Brexit storm today as he pinned his by-election hopes on a lurch to the Left.

The Greater Manchester mayor confirmed that he thought leaving the EU had been 'damaging' but stressed he was not pushing for immediate re-entry to the bloc.

Giving a speech to a Northern investment summit, he hit out at 'Neoliberalism' and 'trickle-down' economics, complaining that wealth had been 'syphoned off' from workers.

Mr Burnham indicated that the North would get more funding at the expense of the South, arguing that the reverse had been true in a political system that had been failing for 40 years. 

The intervention came amid rising anxiety in Labour ranks at the consequences if the Markefield contest – likely to be on June 18 – is lost to Reform. Outgoing MP Josh Simons officially quit this morning, taking on the traditional post of Crown Steward and Bailiff of the Chiltern Hundreds. 

Even fans of Mr Burnham say his chances of success could be worse than 50-50, with polls having consistently shown Nigel Farage's outfit on track to win.

Mr Burnham's allies lashed out today after leadership contender Wes Streeting voiced support for rejoining the EU.

That highlighted Mr Burnham's own strident views on reversing Brexit – seen as deeply unhelpful when he is wrestling Reform in the Eurosceptic seat of Makerfield. Victory would be a springboard to taking over from Keir Starmer.

Sir Keir visited Labour HQ this morning to thank staff for their hard work, insisting he would 'get on with the job'. He pledged to support whatever candidate is fighting Reform at the by-election.  

One despairing minister told the Daily Mail of the Brexit wrangling: 'Day one has gone well but it'll be downhill from here on in.' 

Another senior Labour source said the complaint amounted to 'Wes is doing politics and I'm upset about it'. 'Welcome to Westminster, Andy. It's not all free money and buses with bees on,' they added.

A former minister said: 'Burnham has the political sense of a gnat.' 

Despite the race to replace him being in full swing, Sir Keir is not expected to concede he will have to quit or set out a timetable. Instead, the premier will wait to see whether Mr Burnham can get back into the Commons. 

In other twists and turns today:

• Lord Gove – one of the architects of Brexit – wrote in the Daily Mail that any moves to rejoin the EU would be a 'betrayal';
• Mr Lammy suggested Sir Keir will consider standing down if a leadership challenger gets 81 nominations from MPs;  
• Angela Rayner is said to have turned down an offer to become Health Secretary after Mr Streeting quit;
• Reform could announce a local plumber as its candidate as soon as today;
• There is speculation the Tories could shun Makerfield to maximise the chances of Mr Burnham being defeated;
• The next batch of Mandelson documents will not be released this week, meaning they will appear at the beginning of next month as the by-election struggle reaches its culmination; 

Mr Burnham said areas like Makerfield had suffered from 'the draining away of economic, social and political power from these places left adrift'. 

'That deindustrialisation was then compounded by deregulation, privatisation in the 90s and austerity in the 2010s. It all adds up to 40 years of neoliberalism that have not been kind to the north of England – 40 years of trickle-down economics that did not, in the end, trickle down very much at all to Platt Bridge or Hindley.

'In fact, that system has syphoned wealth out of those places and into the hands of people for whom life was already very good.

'It created an economy that didn't work for most working people. It led to the loss of good jobs, the decline of our high streets, and the neglect of our towns. It led to people paying over the odds for the daily basics energy, housing, water, transport.'

Earlier, Deputy PM David Lammy acknowledged that the 'internecine warfare' after disastrous local elections was a 'spectacular own goal'. 

'Some colleagues are lighting the match and standing in the petrol,' he warned, hinting that a general election could be inevitable if the party does not pull together.

But Mr Lammy refused five times to say whether he personally wanted to rejoin the EU.  

Backbencher Jonathan Hinder said the call to unwind Brexit showed a 'staggering level of out of touch'.

Attempting to rally the party together, Mr Lammy told Sky News: 'This is a Labour by-election. We've got quite threatened votes, Reform will be challenging hard.

'I've known Andy Burnham for over a quarter of a century. We were both proteges of the wonderful Tessa Jowell.

'We worked together all those years ago under Tony Blair. He will be a great addition to parliament for Makerfield. He has my full support.

'I will be up there, much of the Cabinet will be up there of course, the Labour movement will be up there to make sure we win.'

Mr Lammy hinted that if Labour kept up this level of infighting a general election might be unavoidable.

'This is not a sixth form debate, it is delivery on behalf of the British people,' he told BBC Radio 4's Today programme.

While refusing to say whether he personally supported rejoining the EU, Mr Lammy said: 'Our position was set out in a manifesto voted on by the British people… that was just 22 months ago. There will be another opportunity at the next election.

'We have to get on and deliver on their behalf, and I say to colleagues, 10 days of this, fine. I think the British people will forgive us for the introspection.

'Ten weeks of this, and we're in desperate trouble. We'll be out of office, and what we'll be ushering in is Farage.'

Mr Lammy insisted there is 'no contest' for the leadership currently.

'What there is is people like me who've been in the Labour movement for most of my life being crystal clear that unity, pulling together all of us, is what will deliver for the British people,' he said.

'Introspection and internecine warfare – effectively, some of our colleagues lighting the match and standing in the petrol – that is not what's going to deliver for the British people.

'That's not what's going to deliver for the British people. What that will usher in is Farage.'

Mr Streeting, who dramatically quit as Health Secretary last week, signalled he wanted to see Britain return to the EU in a speech on Saturday. 

The Blairite also declared he will stand in any Labour leadership contest. 

Mr Burnham sought to play down his own stated support for rejoining the bloc as he took part in a media blitz across the weekend.

He insisted there was a 'long-term case' for advocating to join the EU, but insisted he was not campaigning on that issue in the by-election.

Nigel Farage has branded the Greater Manchester Mayor 'open borders Burnham'.

The Reform leader told the Mail: 'It's obvious Andy Burnham wants to say one thing to Labour voters in Makerfield while telling Labour MPs something entirely different as he positions himself for power.

'Reform will ensure the voters know exactly where Burnham stands on rejoining the EU.'

Mr Hinder, MP for Pendle and Clitheroe, told BBC Radio 4's Today programme: 'We are just over a week after we took a real beating in our working-class heartlands.

'It's a very long list – we're talking about the Hartlepools, the Grimsbys, Barnsley, places like Wigan, where this by-election is going to be, and we were losing to a party which until recently was called the Brexit Party.

'And to suggest the solution now is for us to reopen that debate is just staggering, and the Labour Party is in an existential crisis, it really is, and the idea that we can reconnect to our working-class base by reopening this debate is just a staggering level of out of touch.'

On a visit to Labour's HQ this morning, Sir Keir told staff he was 'focused on the job'.

He said: 'So, I am focused on the job that I was asked to do, which is to serve my country and to carry out my duties as Prime Minister of this country.

'Delivering for the very many people who voted us into office, who are saying, 'just get on with it, get on with the job, get on with the change that I need to see in my life'. And that is what I am going to be doing.

'We now have an important by-election coming up. It is Labour versus Reform. We will know very shortly who the candidate is.

'Whoever they are, I am going to support them 100 per cent and I want every member, everyone in our movement, to support them. A Labour candidate to beat Reform. That is the fight that we are in.'

Downing Street has declined to repeat Sir Keir Starmer's claim from last week that he would fight any challenge to his position. 

Kemi Badenoch said renegotiating Brexit would be a 'disaster' for the country.

The Tory leader told the Daily Mail: 'What we see before us is a timid and tired Labour Party, exhausted after less than two years in government. Does anyone believe these clowns can negotiate with the EU?

'They're terrified of making any difficult decisions and will only end up giving away power and money just like they did with their terrible Chagos deal and the failed one-in, one-out deal with France.'

She added: 'It will be a disaster for the country and they will reap the whirlwind if they plunge us back into the Brexit wars, ignoring the clear message the country sent in the referendum of 2016 and the elections of 2017 and 2019 – Get Brexit Done.'

She also said Labour should call a general election if a new leader broke the party's manifesto commitments and advocated rejoining the EU.

Writing for the Mail, Lord Gove said: 'The drive towards rejoining is not just acceleration into an economic cul-de-sac, it is also a betrayal of the democratic vote which politicians promised would be honoured and respected.

'After the agonies of the 2017-19 parliament when establishment voices tried to overturn the clear instruction from the people, it would only further undermine people's belief that those who govern us respect our instincts.'

He said Britain should instead make the most of Brexit freedoms in areas where it had a competitive advantage, such as financial services, gene editing, AI and tech.