British Prime Minister Boris Johnson pressed opposition Labour Party leader Jeremy Corbyn on Tuesday to tell voters in next month’s election whether he backs leaving the EU.

Johnson’s main rival in the snap Dec.12 poll has struggled with defining his position on Brexit ever since Britons narrowly triggered the divorce in a 2016 referendum.

Labour’s new official stance is to negotiate a more EU-friendly withdrawal agreement with Brussels and then let voters decide whether to back it or simply stay in the EU.

But Corbyn refuses to say whether he would then campaign for his own deal. Most top members in the party oppose Brexit and have said they would campaign to remain in the bloc.

Johnson’s Conservatives are trying to seize on Labour’s divisions on the defining issue of UK politics.

“Now the time has come for you to come clean,” Johnson told Corbyn in an a letter released by his office.

“Do you believe the results of the 2016 referendum should be respected and the UK should leave the EU?” Johnson asked.

“Would you commit to campaign for your ‘deal’ in a second referendum?” Labour’s Brexit spokesman Keir Sarmer told BBC radio that letting Britons decide what to do about Brexit was a “practical way to break the impasse.”

“It’s not for the politicians... it’s for the people to decide,” Starmer said.

Starmer himself is one of the senior Labour members opposed to Brexit.

Labour is trailing the Conservatives by 11 percentage points in a poll of polls compiled by Britain Elects.

But the field also includes smaller pro-EU opposition parties that could potentially form a post-election coalition with Labour − if they ever agree on who should lead the government.

The anti-Brexit Liberal Democrats came in second in European Parliament polls in May that Britain was forced to take part in because of Brexit delays.

Lib Dem leader Jo Swinson will formally launch her party’s campaign on Tuesday in London.

Her party is currently running in third place with around around 18 per cent of the vote. But she firmly firmly refuses to back Corbyn − the official leader of the opposition − and wants to become prime minister herself.

The Brexit Party of populist Nigel Farage has 11 per cent and will pile pressure on Johnson during the campaign from the anti-European right.

Corbyn will on Tuesday accuse British the Conservatives of attempting to hijack Brexit to unleash a Thatcherite bonfire of regulation, as he seeks to rally core voters put off by Labour’s ambiguous stance on the EU divorce.

In a major campaign speech for a snap election on Dec. 12, Corbyn will lay the groundwork for his centre-left party to campaign as safeguards of Britain’s welfare state and worker protections, after rejecting calls from many senior Labour figures to take a definitive position against leaving the EU.

Prime Minister Boris Johnson will use Brexit to “unleash Thatcherism on steroids,” Corbyn will say in the speech in a suburb northeast of London, referring to former prime minister Margaret Thatcher who privatised many state-owned industries.

Thatcher is a hate figure in many of the working class communities that voted in 2016 to leave the EU, where Johnson hopes to win seats from Labour to build a pro-Brexit majority.

Corbyn, whose party is trailing the Conservatives in opinion polls, will say Johnson’s government would include the National Health Service (NHS) in a post-Brexit US trade deal.

“This threat to our NHS isn’t a mistake. It’s not happening by accident. The threat is there because Boris Johnson’s Conservatives want to hijack Brexit to sell out the NHS and sell out working people by stripping away their rights,” he will say in the speech, according to his office.

They want a race to the bottom in standards and protections.” More than three years after Britain voted to leave the EU, both of its main political parties have suffered from division over Brexit.

But while Johnson has now firmly positioned his Conservatives behind his call to “get Brexit done,” Corbyn has kept Labour’s stance open.

He says if elected he would negotiate a new deal with the EU that would do more to protect workers, then put it to the people in another referendum, alongside the option to stay in the bloc.

Agencies