The former London mayor joined Michael Gove, the justice secretary, and Priti Patel, the employment minister, to pledge new “Australian-style” immigration controls by 2020 which, he said, he hoped would be carried out after a vote to leave the EU on 23 June.
The trio went on a campaign tour of Lancashire, during which Johnson was asked if his proposals amounted to an alternative to Cameron’s administration. Johnson said that was not the plan. “We are not forming an alternative government, we are presenting alternatives to the government,” he said.
However, on several occasions Johnson referred to immigration policies that would be enacted by “the government of the day” and “any government” in power. If the UK were to vote to leave the EU, it is widely agreed that Cameron’s premiership would be in peril.
When it was pointed out to Johnson that he would have to change Cameron’s mind or depose him in order to implement the new immigration plan, he added: “At the moment we are stuck in the EU so it [the immigration policy] is not possible but post-23 June that option will be on the table. What we want to do is take back control over immigration and have more fairness over the way it is done.”
Johnson has long been a favourite to succeed Cameron but his chances of doing so have increased since he backed the campaign to leave the EU, with Conservative members mostly in favour of Brexit.
The immigration policy statement made by the three MPs was first released on Tuesday night. Using the language of an election manifesto the proposal was also phrased as a pledge, rather than merely an option.
“By the next general election, we will create a genuine Australian-style points-based immigration system. The automatic right of all EU citizens to come to live and work in the UK will end, as will EU control over vital aspects of our social security system,” they wrote.
On the campaign tour, Gove, a close political ally of Cameron until the EU referendum campaign, said the aim was to “liberate” the prime minister so that he could fulfil his manifesto pledge to reduce net migration to tens of thousands rather than hundreds of thousands.
“The only way [Cameron] can fulfil that pledge is by leaving the EU,” he said. “He’s the prime minister who sets policy, he will set policy on 23 June but we just want to liberate him to be able to fulfil the manifesto pledge we all stood on.”
Patel told a crowd in Preston that the Brexit campaign was looking to “take back control of our country and our government”.
All the leading campaigners for Brexit, including Johnson, Gove and Patel, claim publicly that they would want Cameron to carry on as prime minister regardless of the referendum result.
Cameron himself is insisting that he would want to stay on to negotiate with Brussels, despite having said he does not want to serve a third term. However, he would undoubtedly come under intense pressure to resign if the country rejects his entreaties to stay in the EU. Some in his party want him to face a leadership challenge regardless of the result.
Remain campaigners led by the prime minister said the immigration plan would be economically disastrous and could even lead to higher levels of net migration. The Australian government tries to increase its population through controlled immigration.
“Australia has more migration per head than we do here in the UK, so I think it’s the wrong approach,” Cameron told BBC Radio 5 Live. “I also think if we were to say to Europeans they needed work permits to come to Britain, European countries would say to us we need work permits to go and work there.”
George Osborne, the chancellor, called the pledge of a points-based system “fantasy politics” that would lead to a rise in net migration.
Downing Street sources called Vote Leave’s policies “completely unworkable” and added: “Above all, it’s not in their power to implement it.”
Sir Nigel Sheinwald, former British representative to the EU, confirmed it could have practical consequences for Britons wanting to emigrate in the future if other European countries apply similar rules to UK citizens.
“I doubt the leave campaign have even bothered to think about this, but the other EU countries are bound to look at reciprocal measures, which could involve Brits having to be fluent in the language before working, living or retiring in other countries in Europe,” he said.
“You don’t need to have been in as many negotiations as I have in Europe to know that Vote Leave’s immigration plans will have far-reaching and serious negative consequences.
“The introduction of this policy could well make life difficult for Brits already living in the rest of Europe. But it will certainly lead to serious restrictions of the right of Brits wanting to live and work on the continent in the future.
Carolyn Fairbairn, CBI director general, said: “The UK already has a points-based system for non-EU migrants. Extending this to Europe would require giving up access to the single market, which would be hugely damaging for our economy.
“In addition, it is important to recognise the £2.5bn tax contribution migrants make to the UK. We must continue to ensure that free movement of labour in the EU remains a right for workers that boosts our prosperity, not a route to benefits.”
Others raised concerns about the tone of Vote Leave’s campaign, with Trevor Phillips, the former chair of the Equality and Human Rights Commission, saying the leave camp’s stance on immigration risks fuelling a resurgence of far-right politics.
Phillips, a board member of Britain Stronger in Europe, said the senior Conservatives “shout fairness but mean exclusion” when they promise to put in place an Australian-style points system.
“I think the Brexit camp is desperate and they have run out of arguments and are really trying to strike some emotional chords of a particularly ugly kind,” he told the Guardian.
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