Experts said the rise could be down to David Cameron's proposed crackdown on migrant benefits. As UK citizens, they would be immune

Thousands of Polish immigrants are deciding to take British citizenship, with approved applications up 1,200 per cent in only five years.

For the first time, Poles are in the top ten nationalities of foreign-born people who are being granted UK passports. In 2013, a record 6,066 applications were rubber-stamped by the Home Office – up from just 458 in 2009.

The phenomenon is unusual because citizens of fellow EU countries do not usually bother to adopt British nationality, since they already have full rights to live and work here.

The change was welcomed by migration campaigners, with MigrationWatch chairman Lord Green of Deddington saying: ‘This is an encouraging sign of the developing integration of the Polish community.’

Experts say one explanation for Poles – who have arrived in unprecedented numbers over the past decade – taking British citizenship is that they have become unnerved by the prospect of Britain cracking down on benefits or even leaving the EU altogether.

By becoming UK citizens, they are insulated from any future changes planned by David Cameron.

The Prime Minister has promised an in/out referendum on Britain’s EU membership in 2017. He also intends to make EU migrants wait four years to get lucrative in-work benefits, such as tax credits.

By taking UK nationality, the Poles will also be entitled to vote in May’s general election.

There are also many examples of Poles marrying British citizens and having children, which might make it more likely they will take British nationality.

Normally, a migrant has to live in Britain for five years before they can apply for citizenship.

Poles first began arriving in significant numbers in 2004, when the EU’s borders were expanded eastwards.

In 2009, when the first of the new arrivals would have been entitled to apply for citizenship, 458 cases were approved.

In 2013 the Home Office rubber stamped 6,066 citizenship requests from Poles, up from 458 in 2009, putting them ninth in national rankings - with India coming in first

This rose to 1,419 in 2010, 1,863 in 2011, 3,043 in 2012 and then 6,066 in 2013 – doubling in a single year. At that rate, as many as 12,000 Poles a year may now be receiving citizenship.

Dr Michał Garapich, senior lecturer at the University of Roehampton’s Centre for Research on Migration – who is Polish – said: ‘People who have started to settle, started to look at their kids or having families, looked at staying in Britain long-term, this is a shift relating to the UK political discourse surrounding the presence of Britain in Europe.

‘They want to secure their political and social rights. The more the Tories bang on about the referendum, the potential exit from the EU, the more it makes Poles feel insecure.

'The more restrictive the language around migration, the more it predisposes migrants to seek naturalisation.

‘I would not be surprised to see a bigger increase once the date of the referendum is set or when David Cameron makes up his mind which way to jump, yes or no.’

In 2013, Poland ranked ninth on the list of countries whose citizens had been granted British nationality.

Top was India with 36,351 approvals, followed by Pakistan (21,655), Philippines (10,374), Nigeria (9,275) and Bangladesh (8,902).

Last night a source at the Polish Embassy in London said the number of Poles applying for British passports was still fewer than 1 per cent of the 800,000 Polish citizens in the UK.

The source added: ‘Some Poles have been in the UK since 2004 so have already got settled, bought houses or apartments here and are simply planning their future in UK, so applying for a British passport is not such a bad idea.’