Lee Anderson’s decision to join Reform UK has prompted calls for a by-election in his Ashfield seat, where he was elected in 2019 as a Conservative.
There is no requirement for MPs to stand down and trigger a by-election if they defect from their original party, as they are formally elected as an individual rather than a party representative.
There have been several attempts to change this, mainly through Bills introduced by backbench MPs, but none has so far successfully made it on to the statute book.
Since the last election, there have been five defections, none of which resulted in a by-election.
But there have been exceptions.
In 2014, Conservative MPs Douglas Carswell and Mark Reckless not only defected to Ukip but also resigned their seats to contest by-elections for their new party.
Mr Carswell was also the last defector to retain his seat at the following general election, winning re-election as Ukip MP for Clacton in 2015.
Prior to that, no defector had kept their seat since 2005 when Sir Jeffrey Donaldson retained Lagan Valley at the general election after leaving the UUP for the DUP.
He said: “It would be pretty reckless for me to suggest a by-election when we could have a general election in May.”
But Mr Anderson has previously backed calls for MPs who switch parties to be required to stand down and fight a by-election.
Reacting to Mr Anderson’s defection, Mr Mangnall tweeted: “Given that Lee Anderson backed and signed my recall motion, stating that if MPs cross the floor to another political party I hope he is calling a by-election.”
Fellow Tory MP Chris Clarkson retweeted his comment, adding: “Just like the last Conservative MP to defect did… Men of principle, all.”
