Britain’s Brexit Party has rejected an electoral pact with the ruling Conservatives, saying it will field 300 candidates in next month's election to force Prime Minister Boris Johnson to deliver on promises of a clean break with the European Union.

Brexit Party leader Nigel Farage speaks during a party rally, as part of General Election campaign trail, in Ilford, Essex, England, Wednesday, Nov. 13, 2019. Britain goes to the polls on Dec. 12. (Photo: AP)

Brexit Party leader Nigel Farage said Thursday the party had to contest the seats to keep pressure on Johnson, rebuffing Conservative arguments that doing so risks splitting the pro-Brexit vote and helping parties that want to remain in the EU. His comments came on the final day for candidates to register for the Dec. 12 election.

"What we've got so far in this campaign is for Boris to promise to change direction, what we now have to do is to hold him to account to make sure we get a proper Brexit, and that's my job,” Farage said.

Britain is holding a national election on Dec. 12 because Johnson wants to security a majority so he can take the UK out of the bloc by the next Brexit deadline of Jan. 31. All 650 seats in the House of Commons are up for grabs.

Johnson has reached a Brexit deal with the EU but has not persuaded enough British lawmakers to pass it. The single-issue Brexit Party, meanwhile, prefers to leave the EU without a deal.

The Brexit Party earlier this week agreed not to run candidates 317 parliamentary seats currently held by Conservative lawmakers after Johnson pledged there would be no further extension of the Brexit deadline. But the Daily Telegraph reported Thursday that Farage rejected a last-minute strategic offer from the Conservatives to only put up token opposition in 40 key seats if the Brexit Party would stand aside in other constituencies.

Currently the Conservatives have 298 seats and the opposition Labour Party has 243. Analysts say to get a majority the Conservatives need to flip Labour seats in the north and east.

Farage noted that “there are very clearly seats in which we are the lead challenger and there are other seats in which they (the Conservatives) are the lead challenger to Labour.” 

“We could have done a deal on that basis, but the priority for the Conservative Party, they do not want the Brexit Party to get seats in Parliament,’Farage said. “They'd rather risk not winning the election than having a Leave majority, a Leave alliance."

The Conservatives fear that voter support for Farage's party could prevent them from winning some closely contested seats, robbing the party of an overall majority in the House of Commons.

Three smaller parties — the Liberal Democrats, the Greens and the Welsh-based Plaid Cymru — have already announced an electoral pact to increase the chances of electing lawmakers who support remaining in the EU. The parties will throw their support behind whichever anti-Brexit candidate in certain districts is the strongest.

The Labour Party, which promises a second referendum on any Brexit deal, has refused to join the so-called Remain coalition. The party's hopes of forming a government may hinge on the Scottish National Party, which is against Brexit but has said it won't support Labour unless Labour promises to allow another referendum on Scottish independence if Labour wins in December.

Johnson on Wednesday used a speech at a car plant to urge voters to back his Conservatives or face a “delay and dither” coalition led by Labour's Jeremy Corbyn and the SNP's Nicola Sturgeon.