Vince Cable has warned it would be a "loss" to the coalition if fellow Liberal Democrat Chris Huhne was forced to quit the Cabinet.
The Business Secretary's backing came after Mr Huhne contacted police offering to help them establish whether he tried to evade punishment for speeding.
Detectives are expected to interview the Energy Secretary and his ex-wife Vicky Pryce in the coming days, amid allegations she was asked to accept penalty points on his behalf in 2003.
Essex Police have yet to take a decision on whether to open a formal criminal inquiry.
Mr Cable said: "It would be a loss if he went. But he is not talking about going.
"He would be a loss because he is a very effective colleague."
Mr Huhne escaped relatively unscathed from an hour's grilling by MPs during Energy and Climate Change questions in the Commons.
The only backbencher to mention the allegations was Labour's Bill Esterson (Sefton Central).
He raised groans from coalition MPs when he preceded a question on electric vehicles with the remark: "I will resist the temptation to ask whether it's easy to stay within the speed limit in an electric car or not."
Mr Huhne remained straight-faced as Mr Esterson made the comment, and Energy Minister Greg Barker chose not to refer to it in his reply.
