Brexit talks between the U.K. government and the main opposition Labour party have resumed after lawmakers returned to work following the Easter break.
A spokesperson for U.K. Prime Minister Theresa May told reporters Tuesday that the talks will "require compromise on both sides."
Asked if the government could agree retaining a customs union wit the EU to secure a deal with Labour, the spokesman said: "You know the prime minister's position with regard to the importance of being able to do trade deals."
A customs union is an agreement that allows partaking countries to set common external tariffs, allowing goods to travel freely between those countries. The draft proposal between the U.K. and EU does not include a customs union as supporters of Brexit say it prevents the right to strike fresh trade deals.
Earlier this month, May agreed another new Brexit date with EU leaders. It delays the U.K.'s departure until October 31, 2019.
But her leadership status is once again under scrutiny after a lawmaker from her own Conservative Party told BBC Radio that she should step down.
"The only way we're going to break this impasse properly is if we have fresh leadership of the Conservative Party," Nigel Evans said Tuesday.
May withstood a leadership challenge from within her party back in December and under current rules cannot face another similar vote for at least 12 months.
However, opponents could reportedly attempt to rewrite party rules in a bid to replace her with a more vocal supporter of Brexit.
The 1922 Committee of Conservative backbench MPS (members of parliament) — an influential group of pro-Brexit lawmakers within the ruling party — are expected to meet on Tuesday afternoon to discuss what steps can be taken to remove May.