Downing Street has described as “speculation” reports that Theresa May is preparing to offer a further £20 billion to help clear the way for Brexit trade talks.

The Sun reported the offer would be made ahead of a crunch Brussels summit in December, when leaders of the remaining 27 EU states will decide whether sufficient progress has been made on the UK’s “divorce bill” – as well as citizens’ rights and the Irish border – to move on to the second phase of Brexit negotiations, dealing with the future relationship.

If confirmed, the £20 billion figure would bring to around £38 billion the total sum Britain is prepared to pay to settle its liabilities – well short of the £53 billion sought by Brussels.

May has so far held back from putting any figure on the financial settlement in public, and it is thought likely that any offer ahead of the December 14-15 summit would come in the form of clearer guidance on what commitments the UK is ready to cover.

The Prime Minister’s official spokesman said reports of a £20 billion figure were “yet more speculation”.

He declined to confirm suggestions from senior MEP Manfred Weber – a close ally of German Chancellor Angela Merkel – that May had indicated a readiness to compromise in a meeting on Wednesday.

The PM set out her determination to secure a unique deal

Following their talks at 10 Downing Street, Weber, who leads the centre-right EPP in the European Parliament, told reporters: “I am more optimistic. There is progress and a will to see progress.”

On the financial settlement, Weber said that while the UK did not have to state a figure at this stage, it did need spell out which of its outstanding commitments to the EU it was prepared to honour.

May’s spokesman described the meeting as “constructive”, adding: “The Prime Minister set out her determination to secure a unique deal for Britain, but one that works in both our interests. She also set out a very clear position in terms of an implementation period that will serve both Britain and the EU, providing clarity for business and others.”

Failure to secure agreement at the December summit would be a major setback for the Prime Minister as the next opportunity for EU leaders to green-light the second phase talks will not be until March.

It would almost certainly prompt demands from hardline Brexiteers for May to walk away from the negotiating table. Shadow chancellor John McDonnell told Sky News: “Our problem is this – we do not know from one day to another what the government’s strategy is or which coalition there is in the Cabinet that is actually ruling the roost at the moment.

“In that way, there’s an inconsistent approach. We have a government in disarray. There’s no way you can negotiate a decent deal when really the government that’s meant to be doing these negotiations is directionless.”

Brexit Secretary David Davis was due to make a keynote speech on Brexit to an economic summit in Berlin yesterday evening.

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