More than 250,000 people will move to Britain EVERY year for at least two decades if voters reject Brexit, think tank warns - and Turkey joining could send ANOTHER 100,000 people every year

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Lord Green, Migration Watch chairman, said the new report was a 'final wake up call' over mass migration

A major think tank today warned net migration to Britain would continue to run at more than 250,000 a year for the next two decades even if Turkey does not join the EU.

If Turkey did join, another 100,000 people could come to Britain each year by the early 2030s, the think tank said. 

Migrant Watch chairman Lord Green said the findings were a 'final wake up call' about runaway immigration that would see Britain's population his 80 million within 30 years.

Vote Leave champion Boris Johnson has repeatedly demanded David Cameron's Remain campaign spell out its vision for how Britain would adapt to a rapidly growing population if it wins on June 23.

A secret plan to open Britain's borders to 1.5million Turks was revealed yesterday after British diplomats said the move would act as a 'symbolic gesture to Turkey'. 

The new research today will reignite the immigration debate at the heart of the referendum battle with just 10 days to go.

Official statistics in May revealing net migration from the EU had returned to record highs turned around the referendum campaign and turned the focus from the economy to borders.

Lord Green said: 'This report is a final wake up call.

'Even leaving aside the prospect of Turkey joining the EU, it shows that net migration could still be running at 265,000 a year in 20 years time. 

'This would bring our population to 80 million within 30 years. If we remain in the EU there will be nothing to stop a continuing rapid increase in our population.

'This would change our country for ever against the express wishes of a very large majority of our fellow citizens.'

In its report, Migration Watch today said its 'central, but cautious, estimate' for total net migration in 2035 was 265,000 people.

It forecast 60 per cent of the people entering Britain would be EU citizens, with the remainder made up of people coming from elsewhere in the world or ex-pat Britons returning home.

The report warned of 'widespread complacency and denial' about the 'likelihood and the impact' of rapid population.  

The figures in the report do not include any impact from Turkey joining the EU, a possibility which has been hotly disputed during the referendum campaign.

Leave campaigners have insisted Turkey joining the EU is inevitable but Mr Cameron has said it will not happy for decades - or even 'the year 3,000'.

Vote Leave campaigner Priti Patel today seized on the report's warnings of higher migration levels in Britain over the next two decades 

Migration Watch estimated around 100,000 Turks a year might come to Britain in a scenario where Turkey did join in 2024 and transitional controls expired in 2031.

And the think tank warned: 'Looking still further ahead it is hard to see how these numbers might come down until the level of East European economies becomes much closer to our own and until the problems that the Eurozone is now facing are overcome.

'Alternatively a serious economic downturn in the UK would reduce the attraction of our labour market.'

Vote Leave campaigner Priti Patel today seized on the figures and said: 'Turkish membership would mean an additional 100,000 people coming to the UK every year – enough, on its own, to break David Cameron's manifesto pledge to reduce migration to the tens of thousands.' 

But former PM Gordon Brown dismissed the Migration Watch findings today, telling the BBC: 'Anybody can produce figures 20 years from now; you’ve got to look at the real world as we are now.

'I believe that in Britain we have managed migration, it is not uncontrolled immigration. I also believe that the biggest problem is going to be illegal immigration.

'I’m not going to give predictions because you’ve got to know the weight of growth of the economy, you’ve got to know what the employment opportunities are, you’ve got to know the level of border control, you’ve got to know how they policing’s going to work, whether we’re going to have boats in the Channel to stop illegal immigrants.

'These are all issues that have got to be taken into account.'

Official immigration statistics out at the end of May revealed net migration to Britain was still running at near all time highs despite Government promises to cut numbers to the tenss of thousands 

Mr Cameron yesterday moved to dismiss the concerns about Turkey, telling the BBC: 'It's simply not an issue, it's a total red herring and the Out campaign know that.

'Some of them have admitted to it, so they should stop frightening people because it's not going to happen.'

In diplomatic cables revealed by the Sunday Times, senior diplomats advised ministers that the EU's proposals to grant visa-free travel to Turkey's 75million population in the borderless Schengen zone could lead to the UK giving the same status to 1.5million 'special passport holders'.

EU officials have also quietly delayed the publication of of documents on the visa-free deal with Turkey until after June 23 to avoid deterring British voters from staying in the EU, according to reports.