Three in every four of those who joined Britain's workforce in the last year were foreign born.

Official figures yesterday showed that the number of foreign men and women in work soared by 334,000 to more than 4million.

However, the number of British-born workers finding employment in the same period - up to the end of March this year - rose by only 77,000.

Official figures yesterday showed that the number of foreign men and women in work soared by 334,000 to more than 4million

The revelation, by the independent Office for National Statistics, will fuel the explosive debate over 'British jobs for British workers'.

Earlier this month, Iain Duncan Smith broke Cabinet ranks by warning that a new generation of young men and women will be condemned to a life on benefits without tougher measures to stem the flow of migrant workers.

The Work and Pensions Secretary said that his expensive back-to-work schemes will fail without stricter controls.

And he urged British businesses to give young people coming off welfare and back into employment a fair chance, and 'not just fall back on labour from abroad'.

Mr Duncan Smith's comments provoked a furious backlash from British business leaders who said that British youngsters were too lazy, ill-educated and lacking the work ethic to compete for jobs.

How the Mail reported Iain Duncan Smith breaking Cabinet ranks over the migrant jobs situation on July 1

They also blamed the welfare system for not encouraging more unemployed British people to find work.

Recent figures show that Britain's population increased by nearly half a million last year, driven by high levels of immigration and rising birth rates.

Between 1997 and 2010, more than half of the rise in employment in the UK was accounted for by foreign nationals.

Sir Andrew Green, chairman of MigrationWatch UK, said: 'It is impossible to look at these figures which show a substantially greater increase in the foreign-born workforce than in the British-born workforce without deducing that there has been a significant impact on the prospects for British workers.

'There no point in being in denial about this.

'British employers surely have a responsibility to consider the wider implications of who they employ.'

The ONS figures showed that UK unemployment as a whole has fallen by 26,000 in the three months to May to 2.45million.

The unemployment rate was 7.7 per cent - down from 7.8 per cent in the previous quarter.

But the numbers claiming the Jobseeker's Allowance jumped by 24,500 to 1.52million - the biggest such increase for two years.

Of those, nearly half a million are women - an increase of 9,500 and the highest rise in women claiming unemployment benefits for 15 years.

Recent figures show that Britain's population increased by nearly half a million last year, driven by high levels of immigration and rising birth rates

Mr Duncan Smith's outspoken comments were highly unusual and were seen as a warning to Prime Minister David Cameron not to give in to Liberal Democrat demands for a softer stance on immigration - an issue that remains close to the top of voters' concerns.

A source close to Mr Duncan Smith said last night: 'These figures are exactly why Iain felt the need to speak out about this.

'We are doing everything we can do to get people into jobs in the short term, but if businesses keep falling back on foreign labour, we are going to face this problem again and again.

'He is very concerned about the impact of this on the economy.'

The ONS yesterday stressed that the figures for the number of non-UK-born people includes individuals who were born outside the country, but also have British nationality.

However, the number of non-UK nationals finding jobs also rose 239,000 from a year earlier to 2.5million.

The employment rate for UK-born people aged from 16 to 64 was 71 per cent, compared with just 67.3 per cent for non-UK-born people.

The ONS statistics are also set to raise questions about the Government's decision to set a cap on the numbers of foreign migrants.

Some Treasury officials are worried about the effect of the cap on tax receipts as the numbers of migrants contributing to the economy and paying taxes continues to increase.

Meanwhile, the ONS figures indicated that the number of new jobs created in the private sector was still outstripping Government job losses with an extra half a million jobs created in the last year.

There was also a drop in youth unemployment among 16 to 24 year-olds by 42,000 to just over 4million.

Chancellor George Osborne had been hoping for a strong boost to employment.

But ministers yesterday admitted the figures showed that the Government still faces a 'big economic challenge'.

Howard Archer, of consultancy IHS Global Insight, warned: 'With the economy going through a very soft patch, the growth outlook muted and increasing job cuts on the way in the public sector, we strongly suspect that unemployment is headed up over the coming months.'