Charles Kennedy has delivered an upbeat assessment of his party's prospects following the Brent East by-election victory.

The Liberal Democrats are in celebratory mood as they gather for their party conference.

Activists and politicians arrived on Sunday to continue their celebrations following the party's victory last week.

And Kennedy said the party was posing an increasing threat to the Conservatives.

"The big problem for the Tories now is that we are the principal challengers to them in very many of their constituencies right across the country," he told the BBC.

Kennedy was welcomed in Brighton by the party's 54th MP, Sarah Teather, who made headlines by taking one of Labour's London strongholds.

Ahead of the conference, Kennedy was predicting with confidence that the party would have a positive week by the seaside.

"I think the mood will be quite good. The party has been working flat out; many spent their summer holidays in Brent," he said.

"I think we will see that mood replicated in Brighton. We are now being seen to be making a positive case and taking it to the government.

"A lot of people feel their sense of trust in the government and Tony Blair has been drastically reduced."

Party organisers have revealed that attendance is 10 per cent up on last year.

The week will begin with a focus on the manifesto for the European parliament elections, where the party hopes to repeat its recent successes.

And Kennedy will take part in an "open mic" question and answers session.

Tuesday sees debates on higher education and the economy.

Human rights and the treatment of British prisoners held at Guantanamo Bay will lead the international debate.

Proposals on homeland security are also on the agenda.

The three issues likely to "cause a punch up", according to the organisers, are debates on smacking children, animal welfare and the monarchy.

The youth and students wing have continued their tradition of tabling motions likely to upset the leadership by calling for the abolition of the monarchy.

Kennedy said he was "relaxed" about the initiative but admitted conveniently he would be unable to take part.

"I do know I'm in meetings that afternoon," he said.

"I think it's a sign of a healthy party that the student wing should be coming up with this. It's a legitimate debate to have. Good luck to them, more power to their elbow."