MPs’ hopes of stopping a no-deal Brexit have suffered a further blow after an expected showdown on Tuesday evening was blocked by John Bercow.

A controversial amendment – to cut off funding to vital departments if the UK crashes out of the EU without an agreement, to make the outcome untenable – was not selected by the Speaker.

It is the second failed attempt by the Commons to stop a no-deal within a month, with some MPs increasingly gloomy that a way will be found with the clock ticking down to the 31 October deadline.

A further attempt is unlikely before MPs return to Westminster in early September – as both Boris Johnson and Jeremy Hunt, the two Tory leadership candidates, ramp up threats to carry out a disorderly Brexit.

No explanation was given for the decision not to select the amendment, put forward by rebel Conservative Dominic Grieve and Margaret Beckett, the former Labour foreign secretary.

Mr Bercow had vowed to help backbenchers challenge the new prime minister, but may have decided the vote, on the so-called government funding “estimates”, was doomed to fail anyway.

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It would have cut off funds for schools, benefits and international aid unless the Commons had granted the next prime minister specific consent for leaving the EU without a deal.

The Liberal Democrats had pledged to support the move, but Labour had simply said it was “sympathetic” ahead of a decision on the day of the vote.

Downing Street had condemned it, saying last week: “We don't know if that amendment is going to be selected at this point. Any attempt to deny vital funding to Whitehall departments would be grossly irresponsible.

“This is government spending for this financial year and funds crucial areas like schools, housing and welfare.”

June’s attempt to stamp on a no-deal Brexit faltered when a Labour motion for backbenchers to seize control of the Commons timetable for a day was defeated.

It is widely acknowledged it will be more difficult to prevent a determined new prime minister crashing out of the EU than when Theresa May made the same threat.

Then, amendable motions had to be tabled each time her Brexit deal was put before MPs – allowing the Commons to legislate – but no new deal is likely to come forward before Halloween.

It leaves the “nuclear option” of moderate Tories toppling their own government by supporting a no-confidence vote, probably triggering a general election.