Tory leadership candidates are threatening to boycott further BBC TV debates over the corporation’s “biased” handling of Tuesday night’s hustings.

A BBC plan for a Question Time programme with the final two candidates, and for one-to-one interviews with Andrew Neil, is in serious doubt as a row about vetting rages on.

It emerged that one of the viewers who was chosen in advance to ask a question during the Our Next Prime Minister programme had a history of making anti-Semitic remarks and of attacking Boris Johnson, while another was a former Labour Party worker with extremist views.

Three of the four remaining candidates’ camps expressed clear reservations about the BBC’s handling of the hustings event, and suggested they would be more likely to agree to a debate on ITV, Sky or Channel 4.

An imam called Abdullah Patel who asked the candidates about Islamophobia on Tuesday’s programme was allowed on the show despite tweeting about politicians “on the Zionist’s payroll” and endorsing the relocation of Israel to the US. He has also said in the past that he had prepared a statement condemning Mr Johnson’s use of language.