EU migrants poured into Britain at the rate of one every 40 seconds last year, according to a bombshell report the Government tried to bury.

The extraordinary revelation that 800,000 EU citizens exploited free movement rules to move to the UK was dragged out of Whitehall following a six-month battle.

The number of incomers is more than the entire population of Tyneside.

Tory ministers campaigning to quit the EU said the migrants - many of them from Eastern Europe - were driving down wages and putting huge pressure on public services. They said even more would come in future as a result of the new national Living Wage.

The ONS has used a new method to estimate combined long term and short term immigration from the EU for last year. The 'headline' long-term figure for 2015 was 260,000

David Cameron was attacked by his own MPs for trying to bury the Office for National Statistics report beneath a major announcement about the future of the BBC.

The MPs, including serving ministers, joined migration experts in arguing it was now clear the true level of mass immigration to Britain from the EU had been ‘undercounted’ for years.

Yet the Government still insisted that its statistics could be trusted. They said that, because not all of the 800,000 migrants stayed for a year or more, they should not all be counted in the official net migration figures.

The ONS said the 800,000 figure was ‘fair’ to use in relations to the number of arrivals last year, though some of the migrants would have left during the year.

Jonathan Portes, the ex-government adviser who fought a six-month battle for the release of the figures said he also believed the ONS was still undercounting - with a possible discrepancy of up to 260,000 over the last four years.

Yesterday’s analysis suggests there were 1,000,400 “long-term” migrants to the UK from the EU between June 2011 and June 2015, which means they stayed for more than a year.

But other figures for the same period show 2,234,000 National Insurance numbers were allocated to EU nationals - a gap of 1.2 million.

The ONS said much of this gap was accounted for by the fact many of those with NI numbers were working or claiming benefits for less than 12 months then going home, so need not be counted.

In doing so, the ONS published for the first time an analysis of the number of short and long term EU migrants combined.

The total number of arrivals from the European Union was 2.4 million from 2011 to 2015.

This was 1.5m higher than the figure for just long term migrants - which officials had previously focussed upon.

Around 1.3 million more NI numbers have been given out to EU citizens since 2010 than are accounted for in official statistics (pictured)

Last year alone, there were a staggering 800,000 arrivals - or one every 45 seconds.

Meanwhile, around 1.3 million more NI numbers have been given out to EU citizens since 2010 than are accounted for in official statistics.

MPs said that, to the man or woman who missed out on a job or couldn’t get an appointment with a GP, it was entirely irrelevant how long the EU citizens stayed for.

In a blistering attack, ex-cabinet minister Iain Duncan Smith said he was astonished that his own Government would attempt to downplay the impact the migrants were having on jobs and housing.

He said that, to the British citizens who missed out as a result of them being here, the fact they went home after less than a year was no consolation whatsoever.

The ex-work and pensions secretary said: ‘They come in, they do hotbedding in bed and breakfasts and things like that, they then take take jobs at much lower rates.

‘This has forced the salaries of people in low-skilled and semi-skilled jobs down so they have suffered directly as a result of uncontrolled borders with short-term migration.

‘I’m astonished that a government, my government, can sit here and say we had a pledge to bring down migration to tens of thousands but it’s all right then because it doesn’t matter how many people come in as long as they don’t stay more than 52 weeks.’

The immigration statistics were released following a long-running argument over whether the ONS is undercounting immigration from the EU - especially Eastern Europe

It was triggered because there are far more National Insurance numbers being given out to migrants than show up in the officials statistics. HMRC spent months refusing to release full date on the NI numbers. It finally caved in after huge pressure from the Mail and other campaign groups,

Employment minister Priti Patel said: ‘These figures - which had to be dragged out of the government - show the scale and impact of immigration from the EU is even higher than

previously admitted. It is out of control - and cannot be controlled as long as we stay in the EU. This puts huge strains on the NHS, housing, schools and other public services.

‘Short term migration is highly significant, and arguably most damaging in terms of wages and work conditions.’

Former London Mayor Boris Johnson on the EU referendum campaign trail yesterday. He has accused the pro-EU camp of being 'dishonest' about immigration

Mr Johnson said politicians had been driven to 'dishonesty' because they did not want to admit they cannot control immigration while Britain is inside the EU. Pictured, migrants break through fences in Macedonia

Last night, it was claimed Tory MPs were so furious at the PM’s handling of immigration that letters demanding his resignation were already being submitted to the chairman of the party’s 1922 Committee demanding his resignation.

One pointed to the fact that, as recently as November, Mr Cameron had claimed action was needed to curb benefit claims by migrants, as 40 per cent of new arrivals were taking money from the State.

The Home Office said that the ONS report was a vote of confidence in immigration statistics.

But Mr Portes, principal research fellow at the National Institute of Economic and Social Research, said while he ‘respected’ the views of the ONS - he disagreed the matter was settled. (MUST)

He pointed to figures buried in yesterday’s study suggesting the number of migrants settling here over the past four years could have been undercounted by up to 260,000.

In a lengthy dissection of the the ONS report, Mr Portes wrote: ‘The evidence suggests that the migration statistics have in fact undercounted EU migration to the UK.’

He said long-term migration figures - people moving to the UK for a year or more - gave a figure of 739,000 arriving in the four years to June 2014.

But, according to HMRC data handed to the ONS, one million people from the EU who had registered in the four years to April 2014 had an active National Insurance Number.

This means they paid tax or received benefits so we’re definitely in the UK.’

Alp Mehmet, Vice Chair of Migration Watch, said: ‘What matters is the increase in the European-born population in Britain which is not consistent with the immigration figures. This ONS report has not addressed that question.

‘This ONS release agrees with our earlier analysis which noted that short-term migration accounts for much of the difference between national insurance numbers and the immigration figures, but not for all of it.

‘We still have no explanation for the increase in the Eastern European population of 90,000 a year over the last four years, when the net migration figures showed only 40,000. We stand by our estimate that EU migration may have been undercounted by as much as 50,000 a year.’

A Government spokesman said: ‘Despite recent questions about the figures, the ONS have now put this issue beyond doubt. As their report explicitly states, national insurance numbers are “not a good measure” of levels of migration.

‘As the Government has consistently pointed out, national insurance numbers can be obtained by anyone working in the UK for just a few weeks, and the ONS explains clearly why the number of national insurance registrations should not be compared with migration figures — because they measure entirely different things. Short-term migrants have never been included in the long-term migration statistics, which are governed by UN definitions.