The European Commission President said Eurocrats were “not naive” about the forthcoming negotiating process – due to begin in the coming weeks.
Some reports suggest the amount could be as high as £52million, but the stark sum is not a “punishment”, Mr Juncker said, and will cover projects the UK has already signed up for, including pensions for EU officials.
Jean-Claude Juncker warned Britain will have to pay an EU exit bill
It will be a bill reflecting former commitments by the British Government and by the British Parliament
Speaking to the BBC, he argued: “It will be a bill reflecting former commitments by the British Government and by the British Parliament.
“There will be no sanctions, no punishment, nothing of that kind.”
The letter will be sent by the prime minister just four days after the EU’s 60th anniversary celebrations in Rome on Saturday.
Eurocrat said he was willing to deal with Britain "fairly"
Asked how he felt about Britain’s pending departure, Mr Juncker said: “It’s a failure and a tragedy.
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“I will be sad as I was sad when the referendum took place in Britain – for me it’s a tragedy.”
Rowing back from his usual hardline stance, Mr Juncker, however, hint he was willing to give Brits a good deal.
“I’m in everything but a hostile mood when it comes to Britain,” he continued. “We’ll negotiate in a friendly way, a fair way, and we’re not naive.”
Blair and Juncker: Together through the years Wed, January 25, 2017
Former Prime Minister, Tony Blair and President of the European Commission, Jean-Claude Juncker have always shared a friendly relationship over the years.
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EU Commission President Juncker greets former British PM Blair in Brussels
Mrs May made clear her top priority is to secure the rights of one million Brits living on the continent as well as the three million Europeans living in Britain.
The commitment was echoed by Mr Juncker, who added: “I am strongly committed to preserving the rights of Europeans living in Britain and the British people living on the European continent.
“This is not about bargaining, this is about respecting your dignity.”