Ming's critics branded 'enemy within' by rival

Bitter infighting erupted today over Sir Menzies Campbell's leadership of the Liberal Democrats.

The party ' s home affairs spokesman, Nick Clegg, launched a ferocious attack on "enemies within".

Specifically mentioning Lord (Bill) Rodgers, one of the party's "grand old men" who had expressed disappointment at Sir Menzies' stewardship, Mr Clegg warned against "doing the spadework of our opponents".

His tough words came as Lord McNally, Lib-Dem leader in the Lords, admitted the battle to succeed Sir Menzies, 66, had already begun, with likely contenders "positioning" themselves for a contest.

Former leader Lord Ashdown issued a blunt warning to leadership hopefuls not to destabilise the party ahead of a general election as it struggles in the polls.

Sir Menzies's predecessor Charles Kennedy, who was ousted early last year after his drinking came to public attention, stressed nothing should be "fazing" his party - interpreted by some as suggesting the current leader had no excuses for the party not doing well.

MPs were stunned by the strength of Mr Clegg's outburst against Sir Menzies's critics, with some suggesting it could only further boost his own standing in the party.

At a fringe meeting at the party's annual rally in Brighton, Mr Clegg - seen by many MPs as the frontrunner to take over as leader - said: "There are plenty of people outside the party who are having a pop at Ming, some, Bill, wittingly or otherwise, do so from within the party.

"I want to warn against enemies within. We drifted down four per cent [in the polls] but it is incredibly important - as we gather together here and as we re-establish a sense of tribal loyalty among ourselves - that we don't ever do the spadework of our opponents."

Mr Clegg stressed that the " enemies within" were people forgetting the party's progress in recent years and people "turning inwards pointing fingers at each other" when the party is under pressure.

His comments highlighted the anger among party members at the comments by Lord Rodgers - one of the Gang of Four behind the Social Democrats - who said the Lib-Dems lacked energy and direction.

Lord McNally admitted there had been "rumblings of discontentî this summer over Sir Menzies's leadership."

The peer added: "I do know there are people who have ambitions to be leader of the party and like all good, prudent politicians are positioning themselves well by speaking at the right fringe meeting, speaking at the right Friday night local party dinners."

He declined to confirm that he was referring to the party's environment spokesman Chris Huhne and Mr Clegg. But Lord Ashdown emphasised to future leadership candidates that the party must remain united behind Sir Menzies.

He said: "There is a time for them and it ain't now. The time now is to get behind the party, prepare for the elections and win.î

Lord McNally insisted that he was not aware of any current plots against Sir Menzies and argued that the possibility of an early election had "concentrated" MPs' minds.

However, another source suggested a challenge could emerge if Prime Minister Gordon Brown delays calling a general election until 2009 or 2010.

Mr Huhne pointedly did not deny that he was now preparing the ground for a second leadership bid, after being beaten by Sir Menzies in the contest last spring.

Asked about Lord McNally's comments, he said: "There is absolutely no vacancy for the leadership."

Party president Simon Hughes also accepted that the jockeying before the official start of a leadership race was already under way. He said: "It has always been the case that people who hope to be leader one day make sure people see them, hear them and come to appreciate them."

His comments followed an opinion poll for the Independent showing the Lib-Dems marooned on 15 points, down seven since April. Labour was on 37 per cent and the Tories 34. The gloomy findings echo a Sunday Times poll which said 63 per cent of Lib-Dem supporters believed the party would do better with a younger leader.