Nigel Farage has ditched plans to take on the Tories in more than 300 seats, after what he said was Boris Johnson's "shift of position" on Brexit.

The Brexit Party leader had planned to run candidates in 600 seats after Mr Johnson rejected his offer of a "Leave alliance" to deliver Brexit.

But he has been under pressure not to split the pro-Brexit vote.

The party will not now stand in 317 seats won by the Tories in 2017, focusing instead on targeting Labour.

The BBC's Alex Forsyth said some Brexit Party candidates had expressed concern about Mr Farage's plan to stand against the Tories in 600 constituencies, fearing it could hand an election victory to Labour and lead to another EU referendum.

Mr Johnson welcomed Mr Farage's move, calling it "a recognition that there's only one way to get Brexit done, and that's to vote for the Conservatives".

But Tory chairman James Cleverly said there was still a "danger" the Brexit Party could split the Eurosceptic vote in target seats, leading to the election of MPs who could "frustrate the Brexit process".

The Brexit Party is less than a year old and does not have any MPs - but it was the clear winner in the UK's European elections in May, with more than 30% of the vote.

Explaining his U-turn to supporters in Hartlepool, Mr Farage said Boris Johnson had recently signalled a "big shift of position" in his approach to Brexit.

He cited a pledge by the PM not to extend the transition period that would follow the UK's departure from the EU. This would see Britain sticking to the European Union's rules on issues such as freedom of movement until December 2020.

Mr Farage also said he was encouraged by recent commitments from Mr Johnson to seek further divergence from EU rules in a post-Brexit trade deal.

He added that this was a "huge change" from the kind of trade pact that had been planned under former PM Theresa May.

'Unilateral Leave alliance'

Labour leader Jeremy Corbyn said Donald Trump "got his wish" when Mr Farage announced his electoral strategy.

He said the Brexit Party leader was offering a "Trump alliance" that would lead to "Thatcherism on steroids" and threaten the future of the NHS.

The US president had previously urged Mr Farage to team up with Boris Johnson, saying they would be "an unstoppable force".

Liberal Democrat deputy leader Sir Ed Davey said Mr Farage's decision "shows the Conservatives and the Brexit Party are now one and the same".

Mr Farage had previously offered to not to stand candidates against the Tories in certain seats if the prime minister changed aspects of his Brexit deal.

But the proposal was rejected by Boris Johnson, who said deals with "any other party" would "risk putting Jeremy Corbyn into No 10".

Polling expert Sir John Curtice said it was "pretty clear" the Tories would benefit from Mr Farage's move, although it was "not as big a boost as we might imagine".

He said Mr Farage's strategy would not provide assistance to the Tories in marginal seats they are hoping to take off Labour.

"Nigel Farage's offer doesn't really give the prime minister the price he would really want, which is a free run against the Labour Party," he told BBC News Channel.

Mr Farage said he had "genuinely tried" to forge a so-called "Leave alliance" with the Tories, but his efforts had gone nowhere.

"In a sense we now have a Leave alliance, it's just that we've done it unilaterally," he added.

Mr Farage has already confirmed he will not be standing himself in the election, saying he wanted to concentrate on helping his party's candidates.

Mr Farage will not contest seats where the Tories are running - a "big step in the right direction", says one Cabinet minister.

"It really clarifies it for a significant subgroup who were still very torn," says another member of the government.

Hypothetically, the decision by the Brexit Party leader makes it notionally easier for the Tories to keep seats they hold already.

But it's a million miles away from giving them a clear run.

Read more from Laura.

Pro-Remain election pact

Scottish National Party leader Nicola Sturgeon said the Conservatives have "effectively become the Brexit Party".

She added that defeating the Tories in Scotland "will help deprive Boris Johnson's increasingly extreme and right-wing party of the majority they crave".

Anti-Brexit parties Plaid Cymru, the Green Party and the Liberal Democrats have agreed not to stand against each other in 60 seats across England and Wales.

Their pact means that, in Wales, two of the parties will agree not to field a candidate, boosting the third candidate's chances of picking up the Remain vote.

In England, it will simply be a two-way agreement between the Lib Dems and the Greens.