Migrants are scrambling to secure British citizenship in record numbers amid fears Labour's looming immigration crackdown could make it far harder to settle permanently in the UK.

More than 312,000 refugees, foreign workers and family dependants applied to become British citizens in the year to March - the highest figure ever recorded and nearly double the level seen eight years ago, according to new Home Office data.

At the same time, a further 331,000 people sought indefinite leave to remain (ILR) - the route that allows migrants to stay permanently before applying for citizenship - over the past two years, marking another record high and a 28 per cent jump on the previous two-year period.

The surge comes as Labour prepares to overhaul the immigration system by extending the amount of time migrants must spend in Britain before they can settle permanently.

Under proposals being pushed by Shabana Mahmood, migrants would have to wait 10 years rather than five before qualifying for ILR unless they are high earners or employed in public services. 

Current plans would also apply the tougher rules to workers already living in Britain.

Experts believe the prospect of stricter rules is fuelling a rush among migrants to secure citizenship while the existing system remains in place.

Dr Nuni Jorgensen, of Oxford University's Migration Observatory, said the spike had exceeded expectations and was being seen not only among non-EU nationals but also among Americans and Europeans already living in Britain.

'One potential reason is the heavy publicity around Government and opposition plans to restrict permanent status and citizenship,' she said.

'In that context, some people may feel it is better to apply for citizenship now rather than risk tougher requirements later,' Dr Jorgensen added.

Under current rules, migrants can apply for British citizenship after living legally in the UK for five years, provided they have not spent more than 450 days outside the country during that period. 

Applicants must also pass the Life in the UK test, prove they can speak English to GCSE level and show they are of 'good character'.

Labour is also considering restricting access to benefits so migrants would only qualify once they become British citizens, rather than immediately after receiving indefinite leave to remain as is currently the case.

The Conservatives have proposed even harsher measures, including forcing migrants granted ILR to wait five years before becoming citizens instead of the current 12 months. 

The party also wants to permanently block anyone who entered Britain illegally from ever obtaining ILR or citizenship.

Reform UK has gone further still, proposing to scrap ILR entirely for most migrants and replace it with renewable five-year visas featuring tougher salary requirements, stricter English tests and no access to welfare benefits. 

Under its plans, only British citizens would qualify for benefits and new arrivals would be banned from holding dual nationality.

The figures underline the lasting impact of the post-pandemic migration boom under Boris Johnson's government, with growing numbers of foreign nationals now reaching the point where they qualify to settle permanently in Britain.

Home Office data shows citizenship applications rose almost 20 per cent in just a year, climbing from 263,440 to 312,063.

Indian nationals made up the largest group of applicants, accounting for 31,298 applications - around one in ten of the total. Pakistanis were the second biggest group with 23,423 applications, followed by Nigerians on 15,747, Italians on 15,130 and Poles on 10,371.

Dr Jorgensen said many EU citizens who had lived in Britain for years without applying for citizenship were now moving quickly because of uncertainty over future immigration rules.

Labour's plans have already sparked a furious backlash within the party, with reports suggesting up to 100 MPs are unhappy about proposals to apply the tougher settlement rules retrospectively to migrants already in the country.

Angela Rayner, the former deputy prime minister, reportedly branded the plans 'un-British' and a 'breach of trust'.

Chris Philp, the shadow home secretary, urged ministers not to weaken the proposals.

He said it was 'shocking' the changes had not been included in the King's Speech, adding: 'I can only conclude that the Government is too scared of its Left-wing backbenchers to implement its own plans.

'Time is now of the essence, and the rules urgently need to be changed. Only very highly skilled migrants who have made a genuine contribution should be able to stay in this country. Low-skilled migrants will have to go home. The Conservative Party will support these changes as long as they are not watered down.'

A Home Office spokesman said: 'The rise in citizenship applications reflects long-term migration trends, with more people now eligible after completing settlement routes. 

'The Home Secretary has set out plans for the biggest legal migration reforms in a generation, tackling challenges created by unprecedented migration levels under the previous government.'