Police are to be asked to investigate sleaze claims against four more peers amid frantic efforts to repair Parliament's tarnished reputation.
Liberal Democrat Home Affair spokesman Chris Huhne said he would be writing to the Yard to request an investigation into the latest four peers caught up in controversy, on the grounds that they might have "contravened the common law offence of bribery".
The party wants Scotland Yard to probe whether Lord O'Neill of Clackmannan, Lord Berkeley, Baroness Valentine and Baroness Coussins broke the law by tabling amendments favouring groups that were paying them, a claim they all deny.
The extension of the cash-for-influence row comes after it emerged ministers were planning a major overhaul of anti-sleaze rules in both Houses.
Justice Secretary Jack Straw confirmed he wanted punishments beefed up so that misbehaving peers could be kicked out.
The measures, being added to the forthcoming Constitutional Renewal Bill, could be retrospective - meaning that they would cover those caught up in the current scandal.
Other disgraced peers with criminal convictions could also face being ejected, including author Lord Archer of Weston-super-Mare and newspaper mogul Lord Black of Crossharbour.
Jeffrey Archer received a four-year prison sentence for perjury and perverting the course of justice, while Conrad Black has been jailed in the US for fraud.
However, Mr Straw suggested that merely changing the rules to allow members of the Upper House to resign could be enough to solve the problem.
"If you had simply provision for peers to resign then I think quite a number of those who were previously convicted would have resigned and that those who face these allegations may, as often is the case in business, for example, have been placed in a position in due course where they had no alternative but honourably to resign," he said.
