Having lost the argument on the economy, Vote Leave has unleashed its inner Farage

Given the scaremongering by the Outers on immigration, David Cameron and George Osborne have no choice but to spell out the economic risks of Brexit with no holds barred

The Outers believed that such tactics might backfire by repelling some liberal swing voters. Something has changed. (Getty)

“We won’t play the immigration card; we’ll leave that to Nigel Farage,” one prominent figure in the campaign to leave the EU told me last summer. The Outers believed that such tactics might backfire by repelling some liberal swing voters. It is why they did not want Farage to play a big role in the Leave campaign.

“The official Out campaign does not need to focus on immigration,” Dominic Cummings, Vote Leave’s campaign director, wrote in 2014 as he mapped out a proposed strategy. He argued that immigration was such a powerful dynamic in public opinion that the Outers didn’t have to shout it from the rooftops. “Focusing on it would alienate other crucial parts of the electorate,” warned Cummings.

Something has changed; barely a day goes by now without Vote Leave doing exactly what it said it would not do. And it is going to carry on doing it until 23 June.

Firstly, the migration crisis – and the EU’s woeful response to it – has made the issue much more potent than it was two years ago. Secondly, Vote Leave has lost the argument on the economy. It has been steamrollered by a constant stream of reports from the Treasury and bodies like the IMF and the independent Institute for Fiscal Studies, warning about the dangers of Brexit. The Out camp can’t name an external organisation that says leaving would bring economic benefits. Thirdly, its plans to counter the In crowd’s blitz by creating a grassroots movement of small businesses fed up with EU red tape have fizzled out.

So there was only one shot left in the locker –immigration. The Out camp's relentless focus on the issue is keeping it in the game. Although the opinion polls appear to be moving in Remain’s favour, both sides believe that immigration could yet drive Outers to the polling booths in greater numbers than less motivated, “soft” Remainers.

Vote Leave has shamelessly linked immigration to the nation’s most cherished institution, the NHS. Priti Patel, the Employment Minister, accuses the In camp of “playing the race card” and yet regularly issues statements such as: “Our membership of the EU is putting the NHS under threat….What we get back from the EU is a city the size of Newcastle (population 288,000) of new immigrants to the UK every year.” No mention, of course, of the 135,000 EU “migrants” who keep our health and social care systems going.

Michael Gove, the Justice Secretary, took the Out campaign to another level by claiming that up to 5.2 million people could come to Britain by 2030 – many from Turkey, even though there is no prospect of that country joining the EU by 2020, as Vote Leave assumes in its calculations. Even if other countries like Serbia and Montenegro joined by then, there could be limits on free movement for seven years.

Thankfully, this nasty Donald Trump strategy did not work for the Tories’ Zac Goldsmith against Labour’s Sadiq Khan in the London mayoral election. (By the way, where is Zac? He seems to have disappeared). But it might work in the referendum campaign. Pro-EU MPs from outside London report that immigration is harming their cause.

So we have two Project Fears in this referendum. Given the scaremongering by the Outers on immigration, David Cameron and George Osborne had no choice but to spell out the economic risks of Brexit with no holds barred. Sadly, everything is either black or white and there is no room for nuance on either side, which does not make for an informed debate. But if the Treasury reports on the short and long term costs of Brexit had included any caveats, these would have been seized on by the Out camp and blown out of all proportion. Why should Cameron and Osborne play softball when the Outers play hardball? They would be fighting with one hand tied by their back and would lose.

Tory Europhobes are furious with the Prime Minister and Chancellor for “misusing the government machine” to pump out pro-EU propaganda. But what did they expect? The Government’s policy is to stay in the EU. When Cameron gave ministers who support Leave the freedom to speak out on Europe, he did not expect them to trash the Tory brand and record by blaming NHS underfunding and the lack of school places on EU migration, or to warn that the £7.20-an-hour national living wage would attract more migrants.

It is easy to portray Cameron as backing Remain because it is the only way he can remain in Downing Street. There is an equally plausible explanation: that he believes EU membership is in the national interest, not least our economic one.

Cameron’s Tory critics say they will never forgive the way he has tilted the playing field against them. If he loses the referendum, he will be forced out sooner rather than later. If he wins, there might be a leadership challenge in an attempt to force him to name his departure date. True, almost half the 330 Tory MPs will vote for Brexit. But most noise about a challenge comes from veterans of the rebellion against John Major after he signed the Maastricht Treaty in 1992. There is a generation gap on the Tory benches. Two thirds of Tory MPs were first elected in 2010 or 2015; many are not obsessed with Europe and would rally behind Cameron after a referendum vote to stay in. So he would survive.

However, by foolishly pre-announcing that he will step down as Tory leader before the 2020 election, Cameron has ensured that the next leadership contest will begin next month, whatever the result of the referendum.