Britain is facing a "divorce bill" of up to 20 billion euro (£18 billion) as the cost of leaving the European Union, it has been reported.
The Financial Times has calculated that more than 300 billion euro (£270 billion) of shared payment liabilities will have to be settled in Brexit negotiations.
The 20 billion euro "upper estimate" was said to cover the UK's share of continuing multi-year liabilities including 241 billion euro (£217 billion) of unpaid budget appropriations, pension liabilities of 63.8 billion euro (£57.5 billion), and other commitments totalling around 32 billion euro (£29 billion).
The FT said its analysis represented the first attempt to quantify the UK's liabilities on leaving the EU, with some officials in Brussels warning that the final figure could be higher.
The Government refused to be drawn on the report. A spokesman said: "As the Prime Minister has said, we will invoke Article 50 no later than the end of March next year. We are not going to provide a running commentary on leaving the EU."
The disclosure may cause further jitters on foreign exchange markets following a tumultuous day for the pound.
At one point on Wednesday sterling lost almost 1% of its value against the dollar during the course of exchanges in the Commons, before staging a rally.
During an at times heated Commons debate called by Labour, a series of Tory MPs lined up to insist that greater transparency was essential to protect British jobs, businesses and investment.
Theresa May has angered many Conservative backbenchers with her refusal to commit to giving MPs a vote on her Brexit strategy despite growing calls for more clarity on the plan before the formal process of leaving the EU is triggered.
May's official spokeswoman said any potential "divorce bill" would be an issue to address in Brexit negotiations.
"If you look at the UK's membership, clearly one element of that is the budget and the contributions," she said. "These issues affect both sides, they affect both the UK and the EU.