The Brexit campaign on Monday sought to regain the initiative after President Obama’s forthright intervention in the EU referendum debate, trying to turn the focus back to the subject of immigration.

After a strong week for the Remain camp, Brexit campaigners have brought out their biggest hitters to attack David Cameron’s EU renegotiation and to claim he had done little to curb the number of migrants travelling to the UK.

Iain Duncan Smith, the former work and pensions secretary, told the BBC on Monday that immigration was “out of control” and that Mr Cameron had failed to get the deal in Brussels he had promised: “My belief is that we didn’t get the reform,” he said.

Michael Gove, justice secretary, said Britain would be subject to a migration “free for all” as the next wave of EU applicants joined the club, a reference to countries including Serbia, Albania and ultimately Turkey.

Mr Gove claimed in the Times that the NHS faced “unquantifiable strain” if Britain remained in the EU.

Meanwhile Boris Johnson, London mayor, added: “The prime minister asked the EU for reform and got two-thirds of diddly squat.

“This is the last chance, in our lifetimes, to take back control and the last chance to take back control of our democracy.”

The interventions were a concerted attempt by the Leave camp to address the reverses of last week, notably Mr Obama’s warning that Britain would go to “the back of the queue” in terms of a trade deal with the US if it left the EU.

Earlier in the week George Osborne, the chancellor, published a Treasury analysis claiming that households would be £4,300 worse off in 2030 than they otherwise would have been had Britain stayed in the EU.

Mr Johnson declined to appear on the BBC to defend his comments about Mr Obama — he said the US president was “part Kenyan” and might harbour a grudge against Britain — but Mr Duncan Smith said he agreed with the mayor.

Referring to Mr Obama’s visit, Mr Duncan Smith said: “I was quite surprised he appeared to be lecturing UK citizens on what should they do in the forthcoming referendum.”