He called the European Commission president a ‘pound shop Bismarck’ after he criticised the UK’s negotiating position.
Mr Rees-Mogg (pictured above), a firm Brexiteer, said Mr Juncker was trying to ‘extort’ money from Britain and compared him unfavourably to Otto von Bismarck, the 19th century politician credited with creating a united Germany.
Mr Juncker has warned there will be no discussions on a potential trade deal between the UK and the EU until progress is made on other issues.
But Mr Rees-Mogg told The Sun: ‘Mr Juncker’s effort to extort money from us shows he is an amateur even at blackmail.
‘Mr Juncker is a pound shop Bismarck, arrogant and bullying but without the charm.’
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Mr Juncker said on Tuesday that he did not think any of the UK’s Brexit papers were ‘satisfactory’ and added that there are an ‘enormous amount of issues that need to be settled’.
He said: ‘We need to be crystal clear that we will commence no negotiations on the new economic and trade relationship between the UK and the EU before all these questions are resolved.’
He said the two sides needed to ‘settle the past before we look forward to the future’.
Meanwhile, Theresa May has insisted the UK is making the running in Brexit negotiations following criticism from Brussels about a lack of clarity from her government.
The prime minister said her government had been ‘coming forward with the ideas’ after Mr Juncker dismissed the position papers published by the UK as unsatisfactory.
Mrs May insisted she remained prepared to walk away from the talks without a deal if what was on offer from Brussels proved unacceptable.
Talks between the UK and the European Union were continuing in Brussels after Mr Juncker expressed his frustration.
His rebuke over the approach taken by Mrs May and Brexit Secretary David Davis came after the EU’s chief Brexit negotiator Michel Barnier said he was concerned about the lack of clarity and insisted: ‘We must start negotiating seriously.’