“My heart goes out to his children.” That was what Nick Clegg said when quizzed about the downfall of his former Lib Dem leadership rival Chris Huhne – whom he once dubbed his “political beast”.

The pair had a famously difficult relationship that became publically strained as they battled it out in the 2007 leadership contest in which Mr Huhne dubbed his rival “Calamity Clegg”.

Mr Huhne’s political career lies in tatters after he admitted perverting the course of justice earlier this month.

The former Energy Secretary’s sudden resignation as MP for Eastleigh has triggered a difficult by-election – threatening the loss of a Lib Dem seat.

But Mr Clegg refused to condemn Mr Huhne.

He said: “I was, like everyone, sort of shocked and saddened in equal measure but you know it’s almost regardless of where you come from in politics your heart has to go out to Vicky and Chris’ children who have been scooped up in all of this. It must be difficult for them to cope with it.”

Despite their differences and Mr Huhne’s damage to the party’s reputation, Mr Clegg said: “I think a lot of people, friend and foe, acknowledge he was a good, hard-working local MP, delivering for things that people cared about.

“I think it is my duty really as the leader of the Lib Dems to look to the future and make sure Eastleigh is properly represented by a hard-working local MP and I am absolutely confident that the whole party can offer that.

“I think what most people will do when they cast their vote is acknowledge who, locally, has the record of delivering good things and who is most credible and promises to do more.”