Desegradation is the buzzword that chills members of both major parties, while local activists fired over Brexit flex their muscles.
Six of the nine former Labor MPs who left the party, dissatisfied with Jeremy Corbyn's leadership and the party's dealings with anti-Semitism, had previously faced local pressure to depose them as MPs.
And the three former Conservative MPs – Anna Soubry, Sarah Wollaston and Heidi Allen – who have given up to join the Independent Group, claim that a "violent wave" of former UKIP members will join local Tory unions in order to just join the Support for Members of Parliament to be deselected by Remain.
Local parties elect candidates for parliamentary elections (sometimes with some help from the party's headquarters) – and they can dismiss a deputy once they have been elected to ensure that they are not under the party banner at the next parliamentary elections in this area.
Local activists argue that MPs should not have the right to a lifelong job and challenge if they do not reflect the views of party members or their constituents.
However, MEPs insist that they have the right to express their views without being thrown out of Parliament.
Deselection is not an easy process, especially in the Labor Party, and MEPs have several weapons at their disposal to fight them.
At present it is not assumed that there are SNP or Lib Dem deputies who are threatened with deselection.
Defector of the work
Four members of the Independent Group – Joan Ryan, Chris Leslie, Angela Smith and Gavin Shuker – had lost their vote of confidence in their constituency in recent months before leaving the Labor Party.
Such voices have no legal force in the party – they are merely a way of giving activists the opportunity to express their dissatisfaction, which in fact encourages the deputies to lift the vote.
After her vote of confidence, Joan Ryan, a former minister under Tony Blair, said: "It never occurred to me that trots, Stalinists, Communists and various leftists would do so [have] Trust in me I have none in them. "
Luciana Berger had also been confronted with a motion of censure, but was withdrawn for allegations – denied by her Liverpool Wavertree party – that she would be "bullied".
Chuka Umunna was also under pressure from activists in his Streatham constituency.
The nine local Labor departments that have called for their withdrawal from the party now have to pick a new candidate for the next election, which they expect to do as soon as possible.
Who else is threatened in Labor?
But it is not just the Labor defectors who have felt the heat: some reports claim that as many as 100 Labor MPs could be challenged as Labor candidates before the next election.
The loyal Jeremy Corbyn loyalist Chris Williamson, who traveled through the country last year with a "Democracy Roadshow" calling for the compulsory re-election of all Labor MPs, was threatened with deselection by members of his constituency Derby North.
Veteran Lab Brexiter Kate Hoey has pledged to combat the vote after losing a vote of confidence in her Vauxhall constituency and her stance on the EU and other issues.
There was some concern among some parties in the party that Labor's latest "democracy review", which proposed changes to the internal structure of the party, would favor the compulsory reelection of all MPs, instead pushing back any decision until after the proposed review of constituency boundaries.
In their letter of resignation, the three conservative defectors said that their former party is subsumed by a UKIP-inspired "purple impulse" that shifts the party to the right, in particular via Brexit.
Broxtowe MP Anna Soubry said she knew of certain deputies who were "scared" and could not vote because they were afraid of voting or being exhorted by their local union.
Before leaving Wollaston and Ms. Allen, both of whom plead for a second referendum, press their views in their local parties. Crunch meetings are planned in the coming weeks.
Who else is in danger in the conservatives?
Of those who remain in the conservative party is a process that can lead to the resignation of former minister Nick Boles, who is behind attempts to prevent a no-deal Brexit in his constituency Grantham and Stamford is underway.
His constituency chairman Philip Sagar has already said that his local members want him out and he "has to go now". But Mr. Boles has vowed to fight all attempts to overthrow him.
A petition demanding that Remain-backed Member of Parliament Dominic Grieve be voted out of the local Beaconsfield Conservative Association has received more than 35,000 signatures.
Sir Alan Duncan is reported by the Telegraph to be exposed to a vote of no confidence organized by Eurosceptic activists at the annual meeting of his association in Melton and Mowbray.
The discontent has even spread to parts of the parliamentary party. Conservative MP Nadine Dorries called for the deselection of some of her more rebellious colleagues, such as Dominic Grieve.
Deselection is not a new phenomenon. In 1904, even the now-announced war president, Sir Winston Churchill, was reluctant to be selected by his club Oldham as a local Conservative opt-out candidate from his election for his support for free trade.
He continued to sit as a member of the city, but joined a few months later the Liberal Party, for which he won a seat in Manchester in 1906.
The recent withdrawal was made by the conservative side. Despite being a member of South Suffolk for more than 30 years, Tim Yeo was rejected as a conservative candidate in 2015 by local members before the parliamentary elections.
Days earlier, MEPs Anne McIntosh of Thirsk and Malton, now in the House of Lords, had suffered a similar fate.
Mr. Yeo and Ms. McIntosh were both prominent chairmen of the committee.
In Labor, actual deselection with the trigger voting system is rare.
Anne Moffatt, a former East Lothain MP, was voted out of office in 2010, while Bob Warring, MP for Liverpool West Derby, blamed a "New Labor Mafia" for his vote in favor of Stephen Twigg in 2007.
How do I remove an MP?
The two main British parties have different rules.
In the run-up to a general election, seated Labor MPs can be made to compete as candidates against all candidates.
However, until recently, they only faced such a new election contest when 50% of local constituencies and affiliates in a constituency voted in a "trigger ballot".
However, at last September's conference, the party made it easier for the deputies to be removed – lowering this threshold to 33%.
In the conservative party, the process is easier.
The acting deputy must apply in writing to be re-elected as a candidate of the party.
This is followed by a specially convened meeting at which the Executive Council votes on the future of the Member of Parliament.
If a petition collects signatures from 50 local members (or 10% of the total membership), this can also force a meeting.
If the deputy loses his vote, he must take part in a new selection of candidates.