Autumn in Westminster is likely to be one of the most exhausting periods of British politics in recent history – late-night votes on Brexit preparations, attempts to thwart no deal, a potential confidence vote in a Boris Johnson administration and an ever-more likely snap general election. But for many Labour MPs, the first thing on their minds is something different – trigger ballots.

In interviews with the Guardian, most MPs said their main frustration was being distracted from preparing for a snap election. MPs said they had set up phone banks, organised multiple dinners and tea parties for local members and set up email campaigns solely targeted at their own members – rather than local voters.

“It has absolutely sucked the oxygen and life out of the Labour party and now we have a whole summer and autumn of introspection when we should be laying into the Tories,” one MP fumed.

Labour MPs have been notified over the past few weeks that votes on whether they must face potential deselection will take place in the next few months – starting with shadow cabinet ministers and frontbenchers from September.

The timing of the vote could mean several shadow cabinet ministers could address the party conference with their future as Labour MPs in doubt.

Some MPs have been notified their “trigger” meetings will take place the week after Labour conference, leading them to cancel plans to attend the event in Brighton in order to spend longer campaigning at home. It is unlikely the process will be completed in time for a snap election in the autumn – or even by May next year.

Labour MPs have always been subject to a trigger ballot, but rule changes agreed in September last year make it easier for an open selection to take place.

If an MP fails to get endorsements from at least two-thirds of the local member branches and two-thirds of local affiliates, such as trade unions, then a full eight- to 12-week selection process will take place – with candidates allowed to run against the sitting MP.

MPs named by their colleagues as likely to be in significant difficulty include areas where leftwing membership is strong, such as London constituencies held by Vicky Foxcroft and Helen Hayes, seats in Merseyside held by Louise Ellman and Maria and Angela Eagle, as well as places with large numbers of new members, such as Thangam Debbonaire’s seat in Bristol West and Peter Kyle’s seat in Hove.

“Thangam has a real problem, particularly given that it’s a massive local party which is very difficult for her to get to know everyone in there,” one MP said.

Other local factors could make a difference. Sources pointed to Birmingham Hall Green, held by Roger Godsiff, the MP who has angered many members by defending parents’ rights to take their children out of LGBT-inclusive lessons.

Many MPs have been quietly getting organised. Labour’s deputy leader, Tom Watson, has run private sessions on surviving the deselection process, with training offered to about 160 MPs who are part of his “democratic socialist” Future Britain group, set up after the departure of seven Labour MPs in February.

Labour’s deputy leader, Tom Watson, has been running private training sessions for MPs on surviving the deselection process. Photograph: Luke Dray/Getty Images

“I do expect to be triggered so I’ve been doing a huge amount of work to compensate,” one Midlands MP said. “I suspect I could win a selection battle, but it’s money and time which could go on fighting to keep this a Labour seat when the Tories are targeting it hard.”

Many MPs said they had compiled detailed lists of members they believed could be counted on to back them. “I’ve got a good idea of the members I think can help me win, people I’ve persuaded to stay in the party, members who I’ve convinced to join, those who have contacted me about stopping antisemitism or campaigning on Brexit,” one MP said.

Another said they were spending time and money on “calls, text messages, emails, social events all over the constituency” and said colleagues were fundraising to cover their costs.

“This is only to try and avoid losing the trigger. The time and costs will go up massively if it proceeds to open selection – that means new leaflets, a website, more phone banks.”

The frustration applies to MPs in both safe and marginal seats, but many also said they felt the party was losing ground attacking the Conservatives because MPs’ headspace was elsewhere. “I have almost 2,000 members who I could take to campaign elsewhere, but we are locked down in the constituency – during the most rightwing government of my lifetime,” one MP said.

Another in a hyper-marginal seat said they knew that any loss of a trigger ballot would be relentlessly used by a Tory opponent. “If I get triggered, then voters in my constituency are effectively being told that my own members may not have confidence in me – and all while an election is looming,” the MP said.

MPs said they were prepared to throw every effort for the next few months into holding their seats. “I don’t do things by halves, if I’m triggered I will be knocking on the door of every single member,” one MP said. “There is no way I would leave it up to chance.”

Within the party’s HQ, there is a lack of sympathy for MPs, especially for those who have only recently begun to desperately engage with members. One source close to Labour’s governing national executive committee said: “The MPs who will be in trouble are ones who have not engaged sufficiently with their members. Some unlucky ones might get triggered but then they should comfortably win their selections,” the source said.

“Member engagement is very important, local councillors have to do it constantly, and it’s something MPs should be doing all the time regardless.”

Momentum, the leftwing grassroots group that has passionately advocated the democratic importance of open selections, has launched a nationwide campaign to encourage members to begin deselection processes for Labour MPs, arguing it can open the door for more diverse, younger, working-class MPs.

The grassroots group said it would support rank-and-file members across the country to begin the process of challenging their sitting MP under Labour’s trigger ballot system.

Momentum’s national coordinator, Laura Parker, has argued the only chance Labour will have to defeat the Conservatives is with “a new generation of young, BAME, working-class leaders who will take on the political establishment and provide a genuine alternative”.

However, the group’s mass campaign on the issue has also sparked some member mix-ups. “Some members are demanding them in seats where they don’t even have Labour MPs and have to be reminded that first they need to help elect a Labour MP and then they can worry about deselecting them,” one party source said.

Should a number of MPs be deselected, party whips are said to be nervous about whether those disgruntled MPs would even stay in the party. A handful of MPs have said they would consider defecting to the Lib Dems or standing as independents.

“I might even be tempted to cause an early byelection and I think I could take a fair few members with me,” one MP said. “But I would never jump before I was pushed – for now I have to try and win this.”