A secret list of BBC sources was leaked to the mayor of Tower Hamlets by a junior staffer working on a Panorama investigation into his time in office.

The list was leaked by a female Bangladeshi journalism student working as a researcher on the programme, who passed it on to the mayor’s office.

Mayor Lutfur Rahman branded the Panorama episode - which airs tonight - “racist and Islamophobic” after seeing the leaked information, which the BBC said includes details of its confidential sources.

He claimed a criminal investigation into the programme is underway, but the BBC said there was no such investigation.

Mr Rahman said: “A dossier passed to us by a BBC whistle-blower has revealed it to be in total breach of the BBC’s editorial guidelines as a public broadcaster.

“It has clear racist and Islamophobic overtones targeting the Bangladeshi Muslim community in Tower Hamlets.”

He added: “The BBC and the undercover production company, Films of Record, have also been referred to the Information Commissioner and there is now a criminal investigation underway.

“The BBC’s targeting of our borough is nothing short of a direct intervention in the outcome of an election.”

A BBC spokeswoman said: “The Mayor’s claims are not true. There is no criminal investigation. We voluntarily notified the Information commissioner after we discovered that a researcher had taken confidential information held by the programme makers and provided it to the Mayor’s office.

“This breach includes material relating to the programme’s confidential sources. Our primary concern is to protect our sources and we are urgently investigating the matter.”

She added: “We strongly reject any suggestion of racial, religious or political motivation in the making or broadcast of today’s programme, which investigates matters of legitimate public interest regarding an elected official.”

BBC Panorama: The Mayor and Your Money airs tonight on BBC One at 8.30pm.