Discipline among Liberal Democrats will have to be "of the highest order" if the party is to overtake the Conservatives, Menzies Campbell has warned.

In an interview with ePolitix.com, the Lib Dem deputy leader said his party had a unique opportunity given the problems faced by both Labour and the Tories.

But he warned against complacency within Lib Dem ranks.

"This is a time of opportunity. It's not a time of certainty by any stretch of the imagination," he said.

"But the gap is there, created by the levels of disappoint with the government and disillusionment with the Conservatives.

"The gap is enormously wide. The question is 'are we able to be disciplined enough and committed enough to fill it?'

"I think we are but we will only achieve what is possible if our commitment and discipline is of the highest order.

"Any hint of complacency and we'll simply get knocked back."

Campbell also dismissed claims that Charles Kennedy's recent reshuffle was a shift to the right.

"It was a reward for competence and ability and it is an effort to make maximum use of the talent that is available," he said.

"I hope it anticipates a return to a more traditional approach of personal freedom about which I feel very strongly."

Campbell, who is also the party's foreign affairs spokesman, also stepped up his attack on George W Bush.

Ahead of the president's state visit to London next month, he said the US administration is failing in its international obligations.

Campbell claimed President Bush had failed to make a positive impact.

"If you draw up a profit and loss account on President Bush's foreign policy you wouldn't need too much creative accounting to reach the conclusion that he had made net losses," he said.

Campbell warned that Bush had damaged the authority of the UN and other key institutions.

"I don't think he's achieved the sort of settlement post-regime change which he envisaged. And there is some doubt as to when or if ever he may achieve such a settlement," he said.

The North East Fife MP also warned that President Bush's focus on re-election meant issues such as the Middle East roadmap would be on hold from the New Year.

"There will be no new foreign policy thinking once we get to the Iowa caucus and the New Hampshire primary in January," he said.

"Bush's profile on this has been of determination to lump states together under the 'axis of evil'.

"It is very difficult to see his administration taking up any position which is inconsistent with that State of the Union address of 2002."

Campbell also predicted that opponents of the US president would find little change from any successor - whether democrat or republican.

"We shouldn't fall into the trap of imagining that a change of administration is necessarily going to bring an immediate volte-face," he said.

"The seeds of 'unilateralism' were sown in Clinton's time. A change of administration will not necessarily mean a sea change in policy."

Campbell also warned that the international community would have to face up to the new threat from the weapons of mass destruction held by Iran and North Korea.

On Iran he said: "We have invested quite a lot in Khatami because he has shown himself to be more progressive. But he does not have universal authority.

"And the more we praise him the more easily he can be characterised as being in the pocket of the West."

"With North Korea, we know it has the missile technology and could be close to having a nuclear capability.

"It's the fusion of these two that would make them very dangerous players."