Dutch prime minister Mark Rutte has dismissed central Brexit promises from the remaining Tory leadership contenders, as he claimed the UK will be a "diminished" country after leaving the EU.

In a sobering interview for the four candidates vying for the Conservative crown, Mr Rutte rejected proposals such as a renegotiation of Theresa May's withdrawal agreement, and a time-limit to the contentious Irish backstop.

His intervention comes ahead of the final round of voting in the parliamentary stage of the contest to replace Theresa May, with Boris Johnson maintaining a clear lead over his rivals.

By Thursday evening, the ex-foreign secretary will be joined by one other rival - either Jeremy Hunt, Michael Gove, or Sajid Javid - to go ahead to a ballot of Conservative Party members in July.

Mr Johnson has pledged in the contest to reopen the withdrawal agreement and ditch the backstop, promising to take the "good bits" from the existing deal and negotiate "alternative arrangements" to the Irish insurance policy during the transition period.

But Mr Rutte replied "no" when asked if there was any realistic prospect of a renegotiation of the deal before the Brexit deadline of 31 October. "What we could do is look together, collectively again at the political agreement which is below the withdrawal agreement - the political declaration," he said.

Who is standing to be the next prime minister? Show all 3 1 /3 Who is standing to be the next prime minister? Who is standing to be the next prime minister? Boris Johnson - 157 votes Foreign Secretary Boris Johnson arriving in Downing Street, London, for a Cabinet meeting where Theresa May will brief on her plans for Brexit before a major speech aimed at helping to break the deadlock in the negotiations with Brussels. PA Who is standing to be the next prime minister? Michael Gove - 61 votes LONDON, ENGLAND - JUNE 07: Britain's Environment Secretary Michael Gove leaves 10 Downing Street on June 7, 2018 in London, England. Prime Minister Theresa May is holding an emergency Brexit cabinet meeting in an attempt to resolve tensions over the UK's Irish border plan. (Photo by Simon Dawson/Getty Images) Getty Who is standing to be the next prime minister? Jeremy Hunt - 59 votes Health and Social Care Secretary Jeremy Hunt leaving Downing Street, London, after attending a Cabinet meeting. PA

Any extension, he told BBC Radio 4's Today programme, would require the future prime minister to outline his plan, "in terms of new elections, new referendums, making changes to the red lines" the UK currently has.

"If nothing is happening, it would mean after 31 October again going through the rounds - then there is no point in having an extension," he said.

On the suggestion of negotiating a time-limit to the backstop, he went on: "Let's go through that idea - you have a time limit on the backstop. That means in four, five, six years time if there is no other solution for the border issue, and I don't think we'll be able to have anything in place in four, fix, six years. Purely technically, and logistically.

"It will be a hard border in your scenario in four, five years. And do we want that? I don't think so because this is the end of the Good Friday Agreement."

And he also made clear that there could not be a transition period if the UK leaves the bloc without a deal, saying: "As Boris Johnson would say, Brexit is Brexit. I would say a hard Brexit is a hard Brexit. I don't see how you can sweeten it."

Pressed whether he is prepared to have a no-deal Brexit, he continued: "No, I hate it. I hate Brexit from every angle, I hate a no-deal Brexit from every angle.

"With a hard Brexit - even with a normal Brexit - the UK will be a different country, it will be a diminished country. It is unavoidable because you are no longer part of European Union, and you are not big enough to have important enough position on the world stage."

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Mr Rutte's comments followed Philip Hammond, the chancellor, warning leadership contenders to set out a Brexit "Plan B" in case their plans falter.

In a speech in the City of London, he will say later today: "It may be that I'm wrong, and a new leader will persuade parliament to accept the deal it has already rejected, or that the European Union does a 180-degree U-turn and re-opens the withdrawal agreement."

In a hint at the possibility of a second referendum, he will add: "If the new prime minister cannot end the deadlock in Parliament, then he will have to explore other democratic mechanisms to break the impasse.