24/04/2016 00:01 BST | Updated 24/04/2017 06:12 BST

Hillary Clinton Hoping UK Will Decide To Stick With The EU

Front-runner for the White House Hillary Clinton has become the latest heavyweight American politician to wade into the referendum campaign and warn against a Brexit vote.

Ms Clinton, who is almost certain to clinch the Democratic Party's presidential nomination, and leads in most polls for the November election to succeed Barack Obama, has made it clear she thinks it would be a mistake for the UK to go it alone.

The former secretary of state's senior policy adviser, Jake Sullivan, told The Observer: "Hillary Clinton believes that transatlantic cooperation is essential, and that cooperation is strongest when Europe is united. She has always valued a strong United Kingdom in a strong EU. And she values a strong British voice in the EU."

The latest foreign intervention came as Leave campaigners launched a furious backlash against Mr Obama, branding him an irrelevant "lame duck" after the US president warned Britain would be at "the back of the queue" for American trade deals if it backed Brexit.

Justice Minister Dominic Raab led the personalised attacks against Mr Obama as the Leave campaign tried to shift the emphasis of the campaign to immigration.

He said: "This is really about a lame duck US president about to move off the stage doing an old British friend a favour.

"I have got no doubt that future US trade negotiators are going to look to other opportunities - I think the British will be first in the queue, not at the back of the queue."

The attack came after Mr Obama set out in stark terms that Britain would not be able to strike a free trade deal with the US "any time soon" if it leaves the European Union (EU) because Washington's focus would be on reaching agreement with Brussels.

Former Tory leader and ex-work and pensions secretary Iain Duncan Smith moved to switch attention to immigration as he insisted the living wage would provoke a "stampede" to Britain from poorer EU nations.

Ukip leader Nigel Farage also savaged Mr Obama's trade deal remarks, insisting the president did not know what he was talking about and was being manipulated by Number 10.

London mayor Boris Johnson stood by his remarks that Mr Obama's comments were "perverse".

At a joint press conference with Prime Minister David Cameron, the president stressed the referendum was a "decision for the people of the United Kingdom" and he was "not coming here to fix any votes".

He added: "I think it's fair to say that maybe some point down the line there might be a UK-US trade agreement, but it's not going to happen any time soon because our focus is in negotiating with a big bloc, the European Union, to get a trade agreement done.

"The UK is going to be in the back of the queue."

Mr Cameron said the referendum was the "sovereign choice of the British people" but added: "As we make that choice, it surely makes sense to listen to what our friends think, to listen to their opinion, to listen to their views, and that's what Barack has been talking about."