Two peers have been suspended from the Labour Party over claims they offered to carry out parliamentary work in return for cash.
Ex-cabinet minister Lord Cunningham and former senior police officer Lord Mackenzie of Framwellgate were recorded by undercover Sunday Times reporters posing as lobbyists.
In a statement, the party said the pair "have been suspended from the Labour Party pending further investigation.
"The Labour Party expects the highest standards of its representatives and believes that they have a duty to be transparent and accountable at all times."
Earlier, Northern Irish peer Lord Laird resigned the Ulster Unionist party whip after being targeted by the same investigation.
All three deny breaching the rules and have referred themselves to the House of Lords Commissioner for Standards.
Lord Mackenzie told Sky News he was "convinced" he had done nothing wrong.
"I understand the rules," he said.
"It is quite clear what you are not allowed to do in the House of Lords, is work for a lobbying company, lobbying ministers to change legislation, putting down amendments for cash, asking questions for cash - that is clearly prohibited."
He said he thought he was being interviewed for a consultant job for a solar glazing company, not as a lobbyist.
The Sunday Times said Laird was recorded setting out ways he could lobby for new laws on behalf of a South Korean solar power firm.
But he insisted he had suspected from the start that they were not genuine.
"In recent days I have been the subject of a scam operated by journalists masquerading as communications consultants," he said in a statement.
"This has led to allegations that I have broken the rules of the House of Lords.
"I wish to make it clear that I did not agree to act as a paid advocate in any proceedings of the House nor did I accept payment or other incentive or reward in return for providing parliamentary advice or services."
On Friday, Tory MP Patrick Mercer quit the party after being targeted by the same investigation.