In his first speech as Liberal Democrat leader, Charles Kennedy has refused to rule out extending links with Labour from constitutional issues to other areas.

He made a point of telling delegates at the party's conference in Harrogate he would leave the possibility open.

The extent of Lib-Lab ties has remained the underlying theme during a week dominated by a spat between Mr Kennedy and his leadership rival Simon Hughes.

The new leader told the party: "We want adult politics.

"We believe that for politics to make a difference, you need to talk to people in other parties.

"It's why I'm talking to pro-European Conservatives.

"It's why I want to maintain our current constitutional co-operation with the government.

"It's also why I won't rule out further co-operation with ministers."

The comments were immediately taken as a signal Mr Kennedy has not let opposition to the strategy of co-operation with the government started by former leader Paddy Ashdown sway his stance.

Lembit Opik MP, a strong backer of increased ties, told BBC News Online: "The speech does look strongly pro-project, which was one of the considerations for people like myself in the leadership election.

"Charles just says it like it is."

Neither Rottweilers nor poodles

Mr Kennedy insisted the Lib Dems would not become poodles, but neither were they Rottweilers who would attack without provocation.

He directed his harshest criticism at the Conservatives, whom he accused of failing to move on from a yah-boo approach to political debate.

"What an irresponsible disgrace they have become on Northern Ireland," he said.

"Loose talk at Westminster can literally cost lives in Northern Ireland.

"We are not going to play Westminster party politics with the Northern Ireland peace process.

"William Hague - grow up."

Mr Kennedy said political parties equally needed to adopt a soberer approach to drugs.

"There's not a family, a home in the land, not touched directly or indirectly by this issue. It's talked about everywhere.

"Except - with a few honourable exceptions - in Parliament. Too much silence in politics, it was once said, is much more ominous than too much noise."

'Too old to rock 'n' roll?'

The Liberal Democrat leader took the government to task for employing the rhetoric of a moral crusade in its pronouncements on home affairs.

He told his party the real moral crusade would be to take a stance against injustice on Third World debt, arms sales and changing attitudes within the United Kingdom towards discrimination.

The new leader poses for the cameras again

He challenged all the main political parties to work together on pensions.

"Parties come and go - tell me about it," he said. "But the reality of the ageing process is a constant.

"Forty this year. Too old to rock 'n' roll? Too young to die? Well, perhaps. But old enough to know that Britain needs to do better.

"Above all, I believe leadership means a serious debate on how you fund public services, so that people understand the costs and options on offer.

"So I challenge the prime minister and the chancellor here and now to use the treasure chest they have now to invest in local schools, local hospitals and pensioners, rather than still more tax cuts for the better off."

'A century of liberal democracy'

Mr Kennedy also told delegates they must bring in one member one vote ballots for all internal party elections.

The switch was one taken by the Labour Party as it remoulded itself into New Labour ahead of the 1997 general election and its prominence in the leader's speech will attract further parallels between the two parties.

But the big debate now is whether he has managed to appear as a convincing leader during a week of photo opportunities and podium appearances.

His authority was questioned early on during the conference by the runner-up in the leadership race, Simon Hughes, who told BBC News Online his rival had "never been a great policy promoter".

The leader ended his keynote address by promising his party he was ready and eager to take it on to greater things.

"The 20th century was too much of a Conservative century," he said.

"The 21st can be the century of liberal democracy."