LONDON (Reuters) - Nigel Farage, the leader of Britain’s upstart Brexit Party, said on Sunday he would not stand in next month’s election, choosing instead to campaign countrywide against Prime Minister Boris Johnson’s EU divorce deal.

FILE PHOTO: Brexit Party leader Nigel Farage is interviewed after speaking during the Brexit Party general election campaign launch in London, Britain November 1, 2019. REUTERS/Peter Nicholls/File Photo

“I have thought very hard about this: How do I serve the cause of Brexit best?” he told the BBC’s Andrew Marr Show.

“Do I find a seat and try to get myself into parliament or do I serve the cause better traversing the length and breadth of the United Kingdom supporting 600 candidates, and I’ve decided the latter course is the right one.”

Farage, an anti-EU campaigner who has stood for parliament unsuccessfully seven times, set up the Brexit Party this year and swiftly won the most votes in Britain in European elections in May.

His announcement this week that the party would contest every seat on Dec. 12 was seen as a potential setback for Johnson.

It risks splitting the vote of Brexit supporters in an election that will once again pit those who want to leave the European Union against those who want to stay, more than three years after Britain voted to quit the bloc in a referendum.

Farage previously led the UK Independence Party (UKIP). The threat that it might siphon off Conservative votes played a major role in persuading then-Prime Minister David Cameron to hold the 2016 referendum.

Johnson, who wants to win a new mandate to enact his divorce deal with the bloc, said he had ruled out a pact with every other party because it would only make it more likely that opposition Labour leader Jeremy Corbyn would become prime minister.

Johnson’s Conservatives are leading in the polls, but with the country still starkly divided over Brexit, the outcome is highly unpredictable.

“NOT BREXIT”

Farage said Johnson’s EU deal was “not Brexit” because it would leave Britain tied to EU institutions and rules.

“If Boris was going for a genuine Brexit, we wouldn’t need to fight against him in this election,” he said.

The government says a withdrawal agreement is the best way to smooth the transition to a future free trade deal.

Voters opposed to Brexit are divided among several opposition parties, while Johnson has aimed to rally Brexit supporters behind his Conservatives.

The pro-EU Liberal Democrats will announce a “remain pact” with the smaller Green Party and Welsh nationalist Plaid Cymru in up to 60 seats in a bid to deny Johnson a majority, the Sunday Times said.

Liberal Democrats leader Jo Swinson told Sky News’ Sophie Ridge on Sunday: “I wouldn’t necessarily assume that the numbers are accurate but we’ve been having those discussions.”

Labour, currently Britain’s biggest opposition party, has said it will renegotiate Johnson’s withdrawal agreement, and then put its deal to the public in another referendum.

Farage, whose party is supported by between 7% and 13% of voters according to recent surveys, said he had wanted to create a “leave alliance”, but his appeals to the Conservatives had gone unheeded.

Johnson, who played a leading role in the 2016 referendum campaign to leave the EU, became prime minister in July after Theresa May failed to win backing for her withdrawal agreement.

He confounded his critics by agreeing a new deal with the EU in October but failed to pass legislation in parliament in time to meet the latest deadline for leaving the bloc, on Oct. 31.

His own failure to deliver Brexit was a “matter of deep regret”, he told Sky News, but his deal was now the only way to get Britain out of the bloc.

“The only way out of the EU now, the only way to get Brexit done, is to go with the deal that we’ve got,” he said.

(This story has been refiled to fix typo in first paragraph to say countrywide, not countywide).