British Prime Minister Boris Johnson's government has urged EU leaders again to drop their opposition to renegotiating the terms of Brexit, claiming recent European elections required a change of approach.

Johnson, who took office late last month, says he wants to leave the European Union with a deal but insists the current terms are unacceptable and if necessary Britain will exit on October 31 with no agreement at all.

In an article in the Mail on Sunday newspaper, Johnson's Brexit Secretary Steve Barclay said European Parliament elections in May had changed the political dynamic and urged EU leaders to amend the mandate of their chief negotiator, Michel Barnier.

"The political realities have changed since Mr Barnier's instructions were set," Barclay wrote.

"Since the last mandate was agreed, 61 percent of all the EU states' MEPs have changed. Such a fundamental shift illustrates the need for a change of approach.

"Mr Barnier needs to urge EU leaders to consider this if they too want an agreement, to enable him to negotiate in a way that finds common ground with the UK. 

"Otherwise, no deal is coming down the tracks."

Former UK prime minister Theresa May quit after delaying Brexit twice while she tried unsuccessfully to get the divorce terms she struck with Brussels through the British parliament.

But the EU has refused to reopen the deal, the result of 17 months of tough negotiations.

Johnson has ramped up preparations for leaving without any agreement.