A MIGRANT influx equivalent to the entire population of Scotland would place “unsustainable" pressure on Britain’s NHS by 2030 unless the country left the European Union, Justice Secretary Michael Gove has warned as Vote Leave placed immigration front and centre of its campaign.

The leading Brexit campaigner claimed the worst case scenario figure of 5.2 million more net migrants during the next 15 years was realistic, even though it assumed Turkey, Albania, Serbia, Montenegro, and the former Yugoslav Republic of Macedonia would all join the EU in 2020 and that the UK would not impose transitional immigration controls on them.

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Mr Gove emphasised how the UK Government’s national living wage - £7.20 an hour now but expected to rise to £9 by 2020 - would act as a pull factor, resulting in "huge additional pressure" on the NHS.

The Scot said that between 172,000 and 428,000 migrants a year would be arriving in the UK until 2030, meaning A&E attendances would spiral by between 6.3m and 12.8m annually, increasing emergency NHS demand by between 28 per cent and 57 per cent.

Denying he was scaremongering, the Justice Secretary said the British Government was in favour of Turkey joining the EU, and Brussels was speeding-up the process.

"Citizens from these countries will inevitably be attracted to the UK, not just because of our free health care but also because of the additional pull factor that will result from the welcome introduction of the national living wage.

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"The European Commission is in the process of speeding-up the accession process. It is already setting up the visa free travel programme with Turkey. That will create a zone of free movement from our borders to the borders of Syria and Iraq," Mr Gove explained.

But Foreign Secretary Philip Hammond suggested his cabinet colleague’s figures were “just plucked from thin air” and designed to confuse, not inform, while Dave Prentis of public sector union Unison, said: "No-one should be taken in by this latest bout of NHS scaremongering from the Brexit brigade.”

The Remain camp highlighted comments by Brexit standard-bearer Boris Johnson, who said in March Turkey would not join the EU "in the foreseeable future" and the idea of 75m Turks having visa-free travel was "simply not on the cards".

Meantime, Vote Leave produced a video challenging David Cameron's insistence that Turkey should not be an issue in the referendum, claiming the UK was currently paying more than £1bn to help Turkey join the EU.

But the Liberal Democrats branded the video "a xenophobic attack from a Leave campaign that knows it is losing the debate".

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Today in a speech to the Fabian Society, the former Labour premier Gordon Brown will urge mothers to vote for Britain to stay in the EU for the sake of their children's future, saying some 500,000 new jobs could be created by opening up the single market further to British firms.

Elsewhere, Jean-Claude Juncker, the European Commission president, warned the UK would not be "welcomed with open arms" by the remaining EU members, if it voted to "desert" the 28-nation bloc.

Ukip leader Nigel Farage, launching his party’s campaign battle bus, which will arrive in Aberdeen late next week, denounced Mr Juncker’s remarks as showing how Project Fear was “moving on to Project Threat”.

He said his party’s campaign would “put open borders, immigration, front and centre of what we’re campaigning about”.

Mr Farage described Boris Johnson as a “good buy”, who would "probably" be the next prime minister if the country opted for Brexit.

The Ukip leader dismissed the celebrity backers, who came out earlier in the day for Remain, dismissing them as “rich luvvies”.

Asked if he had any of his own backing Leave, he said: “Maybe we have, maybe we haven’t. In the Scottish referendum the big celebrities, Andy Murray or whoever it is, you talk to the pollsters made zero difference to the way people voted…The battle lines are clearly drawn this is people versus the political Establishment.”