The announcement cemented Mr Clegg's hold on the parliamentary party, amongst whom he has secured many more declarations of support than his rival, Chris Huhne.

Popular among the grassroots, Mr Hughes' endorsement might also serve to bolster Mr Clegg's popularity among the Lib Dem rank-and-file who will elect the leader next month.

In a statement, Mr Hughes said the party would be in good hands with either of the contenders to succeed Sir Menzies Campbell, who quit suddenly last month.

But he added that he would be voting for Mr Clegg, the home affairs spokesman he encouraged to enter active politics and who had "greatly impressed" him on the Lib Dem front bench.

"Above all I believe that Nick is a great communicator," he said.

"Liberal Democrats will prosper and flourish, not only because we have the right policy and right message, but because we have people who can communicate effectively.

"We must get across urgently the real need for a Britain and a world where liberal values are the norm. In my judgment, Nick will be best able to do this."

Mr Hughes, who stood in the last two Lib Dem leadership contests only to be defeated by first Charles Kennedy and then Sir Menzies, also said he "regretted" there was no female candidate this time around.

Ballot papers will be sent to more than 64,000 members on November 21 and the new leader announced on December 17.