Donald Trump has warned that Jeremy Corbyn would be “so bad” for the UK, while hailing Boris Johnson as “the exact right guy” on the day the two main party leaders kicked off their General Election campaigns.

The US President also called for the Prime Minister and Brexit Party leader Nigel Farage to “get together”, describing them as “two brilliant people” who would make an “unstoppable force”, in what appeared to be a call for them to form a pact.

His comments came as Mr Johnson vowed to deliver Brexit by January at the “absolute latest” if the Tories win the election, and while Mr Corbyn said the Prime Minister alone was to blame for his failure to meet his Halloween deadline to leave the EU.

In a radio interview with Mr Farage on LBC, Mr Trump waded into British domestic affairs by voicing his opinion ahead of the election – a move that has been described by Mr Corbyn as interference.

“Corbyn would be so bad for your country, he’d be so bad, he’d take you on such a bad way. He’d take you into such bad places,” Mr Trump said.

The president said he and Mr Johnson have a “great friendship”, adding that they have “a lot of the same things going”.

He told Mr Farage: “When you are the president of the United States you have great relationships with many of the leaders, including Boris, he’s a fantastic man, and I think he’s the exact right guy for the times.”

General Election 2019
Boris Johnson sits with students as they carve pumpkins at Abbots Green Primary Academy in Bury St Edmunds (Chris J Ratcliffe/PA)

In the wide-ranging interview, Mr Trump also criticised Mr Johnson’s Brexit deal, claiming it hinders trade with the US.

“We want to do trade with UK and they want to do trade with us,” he said.

“To be honest with you… this deal… under certain aspects of the deal… you can’t do it, you can’t do it, you can’t trade.

“We can’t make a trade deal with the UK because I think we can do many times the numbers that we’re doing right now and certainly much bigger numbers than you are doing under the European Union.”

Mr Trump dismissed Mr Corbyn’s warnings that the NHS will be up for grabs for the US after Brexit, suggesting that the Labour leader started the idea.

Timetable for December 12 general election
(PA Graphics)

The president told LBC: “It’s so ridiculous. I think Corbyn put that out there.”

He added: “It’s not for us to have anything to do with your health care system. No, we’re just talking about trade.”

Mr Corbyn responded on Twitter, saying: “Donald Trump is trying to interfere in Britain’s election to get his friend Boris Johnson elected.

“It was Trump who said in June the NHS is ‘on the table’. And he knows if Labour wins US corporations won’t get their hands on it.”

Meanwhile, on the day Britain was supposed finally to leave the EU, Mr Corbyn and Mr Johnson clashed over who was responsible for the continuing deadlock over Brexit more than three years after the referendum vote.

Mr Johnson – who pledged the UK would be out by the end of October “do or die” – was determined to point the finger of blame at a Parliament dominated by Remain-supporting MPs.

“There are just too many people who are basically opposed to Brexit, who want to frustrate it,” he told reporters during a visit to Addenbrooke’s Hospital in Cambridge.

“It was the mandate of the people. They voted by a pretty substantial majority to do this and Parliament has simply stood in their way.”

He said he had an “oven-ready” deal with Brussels which meant the UK would be out of the EU within a matter of weeks if the Conservatives were returned to power in the election on December 12, which was officially confirmed after the Early Parliamentary General Election Bill became law after receiving Royal Assent.

General Election 2019
Jeremy Corbyn kicks off the Labour Party’s General Election campaign at the Battersea Arts Centre (Stefan Rousseau/PA)

However, Mr Corbyn said Mr Johnson had to accept responsibility for his failure to honour the commitment he made during the Tory leadership campaign.

“He said he would rather be dead in a ditch than delay beyond today. But he has failed. And that failure is his alone,” he said.

Mr Corbyn, kicking off Labour’s election campaign with a speech in Battersea, south London, said the only way to resolve Brexit was through a second referendum.

“We need to take it out of the hands of the politicians and trust the people to have the final say,” he said.

“Labour will get Brexit sorted within six months. We’ll let the people decide whether to leave with a sensible deal or remain. That really isn’t complicated.”

Mr Corbyn moved to sharpen the battlelines between the two main parties, highlighting Labour’s “ambitious and radical” programme to transform the nation.

The Labour leader sought to cast the contest as a battle between the “elites” allied with the leader of the “born to rule” and the people.

There were chants of “not for sale” as he pledged to protect the NHS from a post-Brexit trade deal between the Conservatives and US President Donald Trump.