Nick Clegg has said he understands calls for Chris Huhne to return his £17,000 ministerial severance pay but Downing Street refused to comment, saying it was "not appropriate" due to ongoing legal proceedings.
The deputy prime minister said it was up to Huhne to decide whether to refund the taxpayer cash he claimed last year on quitting the Cabinet to fight charges of perverting the course of justice.
Despite repeated vehement denials that he asked his ex-wife to take speeding points for him, the former energy secretary finally pleaded guilty this week and faces jail.
Asked by listeners on his weekly phone-in on LBC whether his fellow Liberal Democrat should repay the £17,000, Clegg initially sidestepped the issue.
Pressed again, he said: "Chris Huhne has got to make that decision but I totally understand why people think, now he's been found guilty and when he's sentenced, that he should pay amends, if you like, for what's happened.
"But at the end of the day, Chris has got to make that decision and at the moment I don't know yet what sentence the judge is going to hand down to him."
Ministers are entitled to severance pay equivalent to three months of their ministerial salary when they leave the Government. However, the money is not paid automatically - it must be claimed by the MP.
Asked by journalists whether the prime minister agreed with Clegg's comments, a Downing Street spokesperson said: "This is a matter for Chris Huhne. It's not appropriate to comment now."
Huhne came under pressure last year not to claim the tax-free payment after becoming the first government minister in living memory to be forced out of office by a criminal prosecution.
Clegg told LBC 97.3 radio: "Chris Huhne hasn't been sentenced yet. He has pleaded guilty. I was as surprised and shocked and saddened as anybody else by his announcement on Monday morning.
"He phoned me on Sunday night. I said to him I thought he had made the right decision.
"He had said what he said beforehand and of course I believed the account he provided beforehand and he then told me on Sunday night that instead he was going to plead guilty.
"He now faces the consequences of that."
Clegg added: "It is for the judge to decide what sentence Chris should face and it is for the people of Eastleigh to decide what MP they should have next, which is why I am keen they should have that choice as soon as possible.
"I feel - and I'm sure everyone feels - for the whole family. It is terrible to see Chris and Vicky's children being dragged into this in the way that they have. The children are certainly innocent, that much is clear."
Asked if he felt let down by Huhne, the Liberal Democrat leader said he expected his former colleague would want to give a full account of events "in his own time".
"I think he will no doubt feel very contrite," said Clegg. "He has stood down as an MP, he is not going to be part of the Liberal Democrats, he won't be continuing in life in politics.
"I am sure he will want to, when he can, express his own feelings about that in his own time.
"I think it is important that we, the Liberal Democrats, get on and get out there in his seat, where actually - whatever the rights and wrongs of what he did - he was actually a very good local MP and worked very hard."