Billboards outside the Conservatives' headquarters in Romford featuring a recently defected MP have prompted a formal complaint to the Electoral Commission.
The local Conservatives have said that they had asked Andrew Rosindell, who defected to Reform UK in January, to take the adverts down after his defection.
Romford Conservatives lodged the complaint with the elections body on Tuesday, after claiming that the billboards are "misleading election communications" as they promote Andrew Rosindell MP along with "Vote Conservative".
They said they have asked Mr Rosindell to remove the signs but that he has refused to do so and threatened legal action against anyone attempting to remove them.
A Reform UK spokesperson said: "This is a bizarre claim and a sign that the Conservatives are losing touch with reality."
Romford Conservatives claim the signs are in breach of the Representation of the People Act 1983 as "being by the Conservatives without official consent from the Conservative Party".
Dominic Swan, chairman of the Romford Conservative Association (RCA), said: "We've been left with no choice. Andrew Rosindell and Reform UK have ignored every request to remove these signs, threatened anyone who's tried to take them down, and is now attempting to fight a local election on a false prospectus.
"Voters going to the polls deserve to know the truth: he is not a Conservative, and his candidates are not Conservative candidates. We're just sick of this farce."
A Reform UK spokesman said: "There is no incentive whatsoever for us to present ourselves as Conservatives - if anything, that would only harm our chances given how toxic the Conservative brand is in Romford and across the United Kingdom.
"Our campaign has been entirely focused on representing local residents and putting Havering first."
Mr Rosindell, who has represented Romford since 2001, lost a High Court bid to be let back into his old constituency office in Margaret Thatcher House in March, having been locked out following his defection.
During legal proceedings against the RCA, Mr Rosindell’s lawyers told a hearing it had "taken the law into its own hands", while RCA barristers stated it was "blindingly obvious" that his licence to use the premises only applied when he was a Conservative.
Mr Justice Choudhury refused the injunction bid, stating Mr Rosindell's case was "intrinsically weak" and that he "ought to have realised that he had surrendered his right to occupy" his office.
He said: "It would have been obvious to him from the moment of defecting that continued occupation would be unsustainable."
