The number of peers in Parliament should be cut by half, Mayor of London and Uxbridge MP Boris Johnson has said.
Johnson's comments come just days after his party leader and close friend David Cameron appointed 45 new peers, 26 of them Conservative, in a bid to rebalance the upper chamber's political make-up.
The House of Lords has now become the second largest legislative body in the world, second only to China's National People's Congress.
Discussing House of Lords reform, he said: "The whole thing has got completely out of control; something radical needs to happen there in the sense of pruning.
"We had a voluntary euthanasia plan in which you were told that you could step down.
"There are a great many of these geezers who don't do much at all. We probably only need about 400 legislators."
Johnson refused to say whether he would ever accept a peerage himself, if offered the role in the future.
The House of Lords came under intense scrutiny last month, after one peer, Lord Sewel, was caught on video allegedly snorting cocaine with prostitutes.
In the obtained footage, the 69-year-old peer argued with one of the women about his daily £200 allowance from Parliament. He calls her "lovie darling" and says: "It pays for this."