Boris Johnson has repeated his threat of walking away from talks with the European Union during a conversation on Saturday with Polish prime minister Mateusz Morawiecki, Downing Street has confirmed.

A Number 10 spokeswoman, issuing a readout of the pair’s phone discussion, said: “On the UK’s future relationship with the EU, the Prime Minister welcomed the agreement on both sides to an intensified process of negotiations in July.

“He said the UK would negotiate constructively but equally would be ready to leave the transition period on Australia terms if an agreement could not be reached.”

The reference was to Australia's bespoke trade deal with the European Union, leading Brexit critics to describe the proposals as akin to leaving on no-deal terms, albeit with a number of mini-deals put in place to allow vital sectors, such as air travel, to continue.

The Prime Minister reflected on the “history of the relationship” between the UK and Poland during a conversation with Polish prime minister Mateusz Morawiecki, a discussion coinciding with Armed Forces Day.

“The Prime Minister spoke to the Polish prime minister today,” said a Downing Street spokeswoman.

“Both leaders expressed regret that they could not meet in person for the annual UK-Poland Intergovernmental Consultations.

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“They endorsed the joint action plan as a blueprint for UK-Polish cooperation over the coming months on issues including defence and trade.

“The Prime Minister and prime minister Mr Morawiecki also reflected on the strength and history of the relationship between the UK and Poland as we look ahead to the 80th anniversary of the Battle of Britain.

“The leaders discussed the shared fight against coronavirus and agreed on the need to ensure a sustainable global recovery where openness and free trade is prioritised.”

Last week Michel Barner said progress on a post-Brexit trade deal between the UK and European Union will depend on whether Boris Johnson stops “backtracking” on commitments he has already made.

However, the EU’s chief negotiator said he believed a deal was still possible as he prepared for an intensified talks process beginning next week.

But “the ball is in the UK’s court” and there must be “clear signals” that progress can be made.

READ MORE: Angela Merkel: Britain must ‘live with consequences’ of looser ties with Brussels

Angela Merkel has warned Britons will have to “live with the consequences” of Boris Johnson rejecting Theresa May’s plan to continue close economic ties with Brussels after Brexit.

The German chancellor spoke with six European newspapers ahead of Germany assuming the rotating presidency of the EU council on July 1, and a day after Mr Johnson’s senior Brexit adviser signalled the next phase of talks with the bloc would be tough.