Labour, the Lib Dems and the Green Party may agree to allow an independent "anti-sleaze" candidate to have a clear run at the by-election triggered by Owen Paterson's resignation.

       Mr Paterson's North Shropshire seat is considered a safe Conservative constituency, with the party having a majority of nearly 23,000 in the 2019 general election. He had been its MP since 1997.

       No date has yet been set set for the by-election, but a Labour source told the BBC it would be "sensible idea" for opposition parties not to split the vote. However, a Lib Dem source told the broadcaster: "The technicalities of having an independent candidate that opposition parties get behind are, frankly, a complete nightmare."

       It is one of three by-elections the Conservative Party will have to contest in the coming months, alongside votes caused by the deaths of Sir David Amess and James Brokenshire.

       The seat has been held by the Conservatives since its creation in 1983, but there is concern among party figures that the furore over Mr Paterson's lobbying activities and wider accusations of sleaze at the heart of the Government will cause a backlash from voters at the by-election.

       Labour has already begun an advertising campaign against MPs who voted for the Leadsom amendment on Wednesday, with social media users seeing a photograph of their MP and the slogan: "One rule for them, another for everyone else."

       Electoral rules say by-elections must be held between 21 and 27 days after the Chief Whip of the party that previously held the seat "moves the writ" – a formal process in the Commons that requires a vote from MPs. Seats are often left vacant for some months, especially if the sitting MP resigns or dies close to a general election.

       On Thursday night, Tory sources confirmed that a by-election in Old Bexley and Sidcup, Mr Brokenshire's former seat, would take place before Christmas. The Conservatives have selected their candidate, Louis French, who is widely expected to inherit his majority of almost 19,000.

       Daniel Francis, a local councillor, will stand for Labour, while Richard Tice, the leader of Reform UK, will stand in an attempt to shave votes from the Conservative majority.

       Party bosses may leave Southend West and North Shropshire, Sir David and Mr Paterson's seats, vacant for months to come. All three seats have sizable majorities, and opposition parties have announced that they will not stand in Southend West out of respect for Sir David, who was killed in a knife attack last month.

       On Thursday, the prospect of a fourth by-election was raised when the former Labour MP Claudia Webbe was given a suspended 10-week prison sentence at Westminster Magistrates Court.

       Parliamentary rules mean she could face a by-election in Leicester East if her appeal fails and 10 per cent of electors in her constituency sign a recall petition to remove her. On Thursday night, she vowed to clear her name.