Germany lined up behind other EU states and official to warn that a new UK prime minister will not be able to renegotiate the Brexit withdrawal agreement struck between the EU and Theresa May.

Michael Roth, the country's EU affairs minister, warned that there was simply no appetite in the EU to re-open talks on the deal.

His warning – a reiteration of previous EU statements on the matter - comes as Tory leadership contenders line up to pledge changes to Brexit and further talks in Brussels.

"I don't see any chances to renegotiate the package, the withdrawal agreement is the withdrawal agreement, and I don't see any appetite to start new negotiations within the European Union," Mr Roth said on arrival for a regular meeting with his EU counterparts in Luxembourg.

Asked whether he thought the UK was "deluded" on the issue, he said: "I don't want to speculate. But the message of the European Union is crystal clear on this issue."

Other EU ministers had a similar message. Sweden's EU affairs minister Hans Dahlgren said he had been watching the Tory leadership race, telling reporters:

"I think our position is clear. This withdrawal agreement is a firm agreement that we stick to. When it comes to the future, the political declaration, we can always accommodate, have a discussion. But on the terms of the withdrawal agreement, that's where we stand."

Asked whether he thought Boris Johnson would make a good prime minister, he replied: "That is not for me to comment."

Arriving at the same meeting, Brexit Secretary Stephen Barclay was silent on the matter of further talks, instead reiterating that the UK would continue to cooperate with its neighbours both inside and outside the bloc.

But back in Westminster the debate is markedly different to the one in Brussels: Mr Johnson, the frontrunner for the Tory leadership, has said he would withhold payment of the £39 billion financial settlement in order to force the bloc to the table.

EU leaders will briefly discuss Brexit at a meeting on Thursday and Friday this week, though they are not expected to reach any formal conclusions or release an official statement.

European Council president and European Commission presidents Donald Tusk and Jean-Claude Juncker are however expected to publicly comment on the latest developments in Britain. The EU regards the issue as now being one for the UK.