LONDON, July 26 (Reuters) A senior British lord quit his post on Sunday and will face a police investigation after a tabloid newspaper released a video showing him semi-naked and snorting white powder through a banknote while partying with two women.

John Buttifant Sewel, formerly a Labour peer and ally of former Prime Minister Tony Blair, stood down from his post as deputy speaker of Britain’s unelected House of Lords after The Sun on Sunday released the footage and accused him of using cocaine and of hiring prostitutes.

Sewel, 69, who is married, could not be immediately reached for comment. Baroness Frances D’Souza, the upper chamber’s speaker, said Sewel had decided to resign as deputy speaker and would be investigated by police. She did not say if he confirmed or denied the allegations.

The imbroglio comes as Britain’s politicians are still trying to regain voter trust after a far-reaching 2009 expenses scandal, and could fuel support for former fringe parties who have styled themselves as anti-establishment.

Ironically, Sewel’s senior position in the House of Lords tasked him with ensuring fellow lords behaved properly. Packed with political appointees from all parties, its role is to scrutinise government legislation, but some politicians on the left believe it is an elitist anachronism and should be abolished.

Sewel’s behaviour was “shocking and unacceptable”, D’Souza said in a statement.

“Lord Sewel has this morning resigned as chairman of committees. The House of Lords will continue to uphold standards in public life and will not tolerate departure from these standards,” she said.

“These serious allegations will be referred to the House of Lords commissioner for standards and the Metropolitan Police for investigation as a matter of urgency.”

The Sun on Sunday said Sewel had disgraced himself and parliament and said that Westminster, the seat of parliament, sometimes seemed as if it was “a giant cesspit of moral, financial and sexual corruption.”

“His behaviour reeks of the sense of entitlement so widespread in our political class,” it wrote.

“The Deputy Speaker of the House of Lords should be a figure of respect and unimpeachable character. Not a low-life.”

The scandal follows a press campaign aimed at John Bercow, the speaker of the House of Commons, over what his critics say are his excessive expenses.