The government has confirmed by-elections will take place next month in two Conservative-held constituencies.
Chief Whip Simon Hart issued writs for the vacant seat of Wellingborough to replace Peter Bone, suspended from the Commons in a sexual misconduct scandal.
Chris Skidmore, who resigned over the government's energy plans, will also be replaced as MP for Kingswood.
The by-elections must take place within 27 days of the writ, and are expected to be held on 15 February.
Mr Skidmore said he had "no regrets" over leaving Parliament.
The former MP for Kingswood, near Bristol, formally quit Parliament on Monday after announcing last week that he was resigning the Conservative whip over the government's plans to issue new oil and gas licences.
Mr Skidmore said he had become increasingly at odds government policy on the environment over the past 18 months.
Labour have already started campaigning in Mr Skidmore's seat. The party's candidate is Damien Egan, the sitting mayor of Lewisham, who grew up in the constituency.
Mr Skidmore took the seat from Labour in 2010 and secured an 11,000 vote majority in the 2019 general election.
Wellingborough election
Parliament's behaviour watchdog found Mr Bone had exposed himself to an aide and physically struck him. Mr Bone denies the allegations.
The 71-year-old was first elected for Wellingborough in 2005, growing his party's share of the vote to an 18,500 majority in 2019.
But Prime Minister Rishis Sunak has admitted the by-election would be "difficult" for the Tories. The majority is smaller than those the Tories had in both Tamworth and Mid Bedfordshire, which were both lost to Labour in by-elections last year.
Mr Bone could stand as an independent candidate. But this is unlikely as the Conservative Party has selected Mr Bone's partner Helen Harrison as its candidate.
Gen Kitchen will be standing for the Labour Party and Ana Savage Gunn will represent the Lib Democrats.
