In a highly provocative speech in Brussels, the European Commission President insisted the UK could not expect a "cut-price or zero-cost" Brexit.
EU sources suggested a divorce settlement set to cost British taxpayers up £51billion was being prepared with payments spread over four years after the country quits the bloc.
MPs and MEPs were enraged by the cash demand from the top Brussels bureaucrat last night.
Tory backbencher Nigel Evans said: "Mr Juncker has shown himself to be an aloof and arrogant bully.
"If we are going to start talking about the settlement, then what about the buildings we have contributed towards over the last 43 years?
"The bill for those will run into billions and we should get our share back."
Tory backbencher Nigel Evans has branded Jean-Claude Juncker a 'bully'
Mr Evans said the Eurocrat's aggressive stance ahead of the negotiations risked losing the support of other EU member states.
Mr Juncker has shown himself to be an aloof and arrogant bully
"The rest of the EU should be asking whether this unelected bureaucrat is the right man to be at the head of their organisation.
"If he carries on like this, he is going to bring about the destruction of his dream of a federal Europe."
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And in a swipe at Mr Juncker's famed love of quaffing fine wines, Mr Evans added: "As far as the divorce settlement is concerned, perhaps we should send him a case of champagne."
Ukip MEP Gerard Batten, the EU exit spokesman for the anti-Brussels party, said: "If Mr Juncker wants to play this game, we should respond tit-for-tat and send him a massive bill for the lost fishing rights over the last 43 years, the extra costs of the Common Agricultural Policy and for the cost of lost jobs and prosperity as a result of Brussels regulations on business."
Mr Juncker's demand for a swingeing departure bill for Britain came in a speech to members of the Belgian parliament today.
The Chief Eurocrat called for Britain to be hit with a 'hefty' Brexit bill in a speech in Brussels
"Our British friends need to know – and they know it already – that it will not be cut-price or zero-cost," said the Commission president.
"He went on to use a French slang term that translates as "salty" and means large or costly.
"The British will have to respect the commitments which they played a part in agreeing.
"Therefore the bill will be – to use a rather vulgar term – very salty. It will be necessary for the British to respect commitments which they freely entered into."
Mr Juncker repeated the commission's demand that withdrawal arrangements – including the divorce bill – must be agreed before a deal covering Britain's future trade relations with the EU can be discussed.
And he claimed talks about the trade deal will stretch far beyond the expected two-year exit negotiation period set out under the EU's Article 50 departure rules.
"This will be a difficult negotiation, which will take two years to reach agreement on the exit arrangements.
"To agree on the future architecture of the relations between the UK and EU, it will need years," the commission president said.
He also restated the commission's insistence that the UK cannot remain a member of the European Single Market without signing up to full free movement for EU citizens, a point already accepted by Prime Minister Theresa May.
"Those who want to benefit from the advantages of the single market must respect the four fundamental freedoms, including the one which relates to the movement of workers," he said.
Mr Juncker described Brexit as 'a crisis which concerns us all'
Mr Juncker described Brexit as "a crisis which concerns us all" and said that it made him personally "sad" to see a major European country leave the EU.
He said: "We need to settle our affairs not with our hearts full of a feeling of hostility, but with the knowledge that the continent owes a lot to the UK.
"Without Churchill, we would not be here – we mustn't forget that, but we mustn't be naive.
"Our British friends will need to understand that we want to continue to develop European integration."
Officials say the bill is being drawn up to cover the UK's share of the cost of projects and programmes which it signed up to as a member of the 28-nation bloc as well as outstanding pension costs for EU officials.
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Continued cooperation with the EU to tackle terrorism and international crime.
A 60billion euro (£51billion) figure was understood to have been discussed at a recent meeting of senior EU figures.
Some leaders including German Chancellor Angela Merkel are reported to be arguing that Britain's exit bill should be lower than maximum floated at the meeting.
Michel Barnier, the commission's chief Brexit negotiator was said to have discussed the idea of spreading the payment of the bill from 2019 to 2023 at the meeting.
EU officials fear the UK's departure from the bloc will leave a gaping hole in Brussels finances by cancelling British payments of the annual membership fee.
They hope that a large bill paid in several instalments will at least soften the blow resulting from the lost UK contribution.
A spokesman for Theresa May said 'we haven't yet begun the process of negotiation to leave the EU'
Downing Street officials snubbed Mr Juncker's demand last night.
A spokesman for Mrs May said: “The simple fact is we haven't yet begun the process of negotiation to leave the EU. We're confident we will get a deal along the lines that the Prime Minister has set out.
“Obviously that will involve, once we have left the EU, decisions on where taxpayers money is spent being taken here.
“We go into these negotiations in a mature and open way and in a spirit of goodwill to get a deal that works not just in our best interests but also for the other member states because it's in our interests that they thrive and prosper alongside us."