"I don't recognise the figure," said May's official spokesperson when asked about the figure published by 'The Sunday Telegraph', quoting three separate sources within the British civil service and government with knowledge of the UK's Brexit negotiating strategy.
"As the secretary of state for Exiting the European Union has made clear, we will meet our international responsibilities but the UK will not pay more than it needs to," added a UK government spokesperson.
His fellow MP Peter Bone also said it would be "very strange" for Parliament to vote in favour of such large sums.
The paper had claimed that UK government negotiators for Britain's exit from the European Union have been able to ascertain that the EU's actual opening position is around 60 billion euros - not 100 billion euros as previously suggested.
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"The 27 say they can't knock off the bits of their 'bill' until the very end - but politically we can't move on money until the 27 member states start to show compromise. As a negotiation process, it just doesn't work," a senior civil servant based at Whitehall in London told the newspaper.
Asecond Whitehall source confirmed the UK bottom line was "30 billion euros-40 billion euros", while a third political source put the figure in May's mind at "north of 30 billion euros".
British Brexit negotiators concluded after second-round talks last month that the EU had created a non-negotiable stanceby refusing to talk about trade until it had reached a settlement on citizens' rights, money and Northern Ireland.
EU budget commissioner Guenther Oettinger told Germany's 'Bild' newspaper today that Britain would remain bound by some previous commitments to long-term projects after Brexit and "will therefore have to transfer funds to Brussels at least until 2020".
He has forecast that in the long term, Britain's withdrawal from the 28-member economic bloc will mean a loss of about 10 to 12 billion euros per year to the EU budget, which will be made up through a combination of cuts and higher payments from other members.