London: A senior peer in Britain's House of Lords was forced to resign on Tuesday after being caught on camera allegedly snorting cocaine with two prostitutes in his flat.
Lord John Sewel, 69, had been part of a 'Sun on Sunday' video expose over the weekend and pressure had been growing on him to step down.
In a letter to the Clerk of the UK Parliaments, he wrote "I want to apologise for the pain and embarrassment I have caused".
He said he hoped his decision would "limit and help repair" the damage.
Scotland Yard have also launched a criminal investigation and searched a property in central London.
The Metropolitan Police said it was looking into "allegations of drug-related offences involving a member of the House of Lords".
Speaking in Singapore, Prime Minister David Cameron welcomed Lord Sewel's decision to "absent himself".
Yesterday, the peer requested a leave of absence from the Lords, but sources had suggested he did not plan to quit.
But in letter published today, he wrote "The question of whether my behaviour breached the Code of Conduct is important, but essentially technical".
"The bigger questions are whether my behaviour is compatible with membership of the House of Lords and whether my continued membership would damage and undermine public confidence in the House of Lords. I believe the answer to both these questions means that I can best serve the House by leaving it," he wrote.
In the 'Sun' footage, Lord Sewel?- who had been deputy speaker of the Lords - was seen snorting white powder from a prostitute's breasts. He was also pictured wearing an orange bra and leather jacket as he reclined, smoking a cigarette.
Footage showed him making disparaging remarks about a number of senior politicians, including the prime minister.
Although Lord Sewel has resigned from the House of Lords he keeps the peerage he was given by the then Labour leader Tony Blair in 1996.
Baroness Stowell, the leader of the House of Lords, welcomed Lord Sewel's decision to step down.
She said, "For the House of Lords to earn the confidence of the public, all of us must respect the privileges that come with a peerage and recognise that - because we are unelected - it is especially important to meet the standards the public have a right to expect, and to act swiftly when we fail".