Tory MPs plotting to topple Theresa May are still struggling to muster enough numbers to trigger a vote of no confidence in her leadership.

The putative rebellion against the Prime Minister faced ridicule after it emerged that backbenchers had again failed to get the required 48 names needed to start the process of ousting her.

Amid signs of dissent over tactics within the backbench Brexiteers’ European Research Group (ERG), a meeting of the so-called ‘Pizza Club’ of unhappy Cabinet ministers also failed to take place.

No.10 also managed to build bridges with senior Leave campaigners over possible protections for Northern Ireland after the UK has quit the EU.

Former Tory leader Iain Duncan Smith, Ulster Unionist leader David Trimble, and former Environment Secretary Owen Paterson all took part in a Downing Street meeting to discuss fresh technological solutions to the problem of keeping open a border with Ireland.

With the PM agreeing to keep open channels of communication, some Brexiteer sources suggested that May had done enough to avoid a confidence vote at least until later this week, when she is expected to meet Brussels chief Jean-Claude Juncker.

So far, just 26 MPs have publicly declared that they have written no confidence letters – just over half of the total needed for a challenge.

Under party rules, a confidence vote can only begin if 15% of all Conservative MPs write personally to backbench 1922 Committee chairman Sir Graham Brady.

He can only accept letters delivered to his office, rather than emails or texts, and as MPs returned to Westminster after a weekend break, some plotters had hoped for a breakthrough.

But Brady, who has a duty to inform Downing Street if the vote is triggered, has still not announced the threshold has been passed.

Jacob Rees-Mogg started the attempted coup last week and former Brexit minister Steve Baker swiftly declared that the rebels had the 48 letters needed, with a dozen more to spare. Baker then admitted that his numbers may have been ‘inaccurate’ as some MPs may have misled him.

On Monday, fellow Brexiteer Simon Clarke again ramped up expectations by claiming that by the end of the day the crucial threshold would have been reached. “It is quite clear to me that the captain is driving the ship at the rocks,” he told BBC Radio 4. “This is the day we stand at the bar of history.”

In the end, just one extra backbencher – Kettering MP Philip Hollobone – revealed he had written a letter.

Clarke later told BBC2′s Newsnight: “I think it is fair to say that the process continues. I don’t take back those words, I hoped today would be the day. There will be other flashpoints.”

Several MPs told HuffPost UK that a heavy whipping operation over the weekend, urging wavering backbenchers to hold off until they saw the final political deal with Brussels at a summit next Sunday, had proved effective.

One ERG source said that it was clear that some colleagues had decided to wait for the ‘meaningful’ vote on the final deal in the Commons. If the PM lost that, several MPs had made clear they would then send in letters in a bid to force her to quit. 

“Baker and Rees-Mogg have totally miscalculated this. Since when do you telegraph to the Chief Whip that you are going to come after the Prime Minister?” one MP said.

“They’ve made us look like rank amateurs,” another Brexiteer said. “There are some people who just don’t want to be seen allied closely to Andrew Bridgen [the backbencher who has long criticised May].”

A senior Brexiteer added: “It’s the most important lesson in politics: if you say you’re going to do something, you have to do it. But it [the 48 threshold] will happen sooner or later.”

Downing Street is still on high alert for any no confidence vote, knowing that it would ruin all the PM’s preparations as she tries to nail down the final pieces of her Brexit deal.

But No.10 has been buoyed by support from across the party, with several MPs suggesting that even if a leadership challenge was triggered then May would easily command the 158 MPs needed to win a simple majority.

Environment minister Therese Coffey predicted she would “win it convincingly”, adding that it was an “unnecessary distraction”.

Former Cabinet minister Nicky Morgan, who chairs the Commons Treasury committee, even suggested May’s hopes of winning the Commons vote on her deal had been boosted by the failure of the plotters to get their promised numbers.

“It looks like the 80 votes against the deal which were talked about on Thursday look wildly optimistic if these 48 letters have proved hard to come by. I think the Prime Minister would win it,” she said.