Former Labour mayor of Newham Sir Robin Wales and ex-councillor Clive Furness have joined Reform UK.
Furness has been selected as the Reform's candidate for mayor of Newham, while Sir Robin will act as the party's London director of local government.
Announcing the move at a press conference alongside Reform leader Nigel Farage, Sir Robin, who was the UK's longest serving mayor when he was deselected by Labour in 2018, said the party had "a lot of rough edges" but represented a chance to "transform our society".
Furness said the "balkanisation of Britain", with people voting along religious and racial lines, was among the reasons he was joining Reform.
He said Labour had "failed London" and the party was "completely out of touch with the communities it was meant to represent".
Furness, who spent more than two decades as a councillor in Newham, added that the party had "abandoned its core principles" and the working class.
Sir Robin said that under mayor Sadiq Khan, London had seen "soaring crime, failing services, and a party that prioritises the wealthy elite over the working class it was built to represent".
As mayor of Newham, Sir Robin oversaw the regeneration of the east London borough as part of the 2012 Olympics.
However, his leadership style also faced criticism and he was ousted by Labour members after 23 years in power.
A London Labour spokersperson said Reform were "scraping the barrel" with the announcement.
"Neither men have been part of the Labour movement for some time. In Newham, Robin Wales was removed by local members following concerns about his record in office," they said.
Reform is hoping to make gains in the capital in May's local elections, when council seats across all 32 London boroughs are up for grabs.
Newham Council is currently run by Labour, which holds the vast majority of seats, while Reform does not currently have any representation on the council.
Farage, who had teased the prospect of a major Labour defection to Reform, said talks were ongoing with a number of other figures who had held senior positions in the party.
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