Charles Kennedy hailed the importance of "constructive dialogue" between the Liberal Democrats and the TUC in his speech to delegates in Blackpool.

Mr Kennedy, the first non-Labour political leader to address the Trades Union Congress, said a "significant proportion" of union members now regularly voted Lib Dem.

I believe that the momentum of public opinion is swinging towards both of us

Charles Kennedy

He stressed that there was a "emerging consensus" between the two sides, as he revealed he had been "a lifelong believer in trade unionism".

Mr Kennedy's speech comes on the day the unions delivered another assault on Tony Blair's plans to bring private companies into the public sector.

And it coincides with a debate on the euro which is expected to see some of the biggest unions opposing the TUC's official pro-single currency line.

'Fruits of cooperation'

Mr Kennedy sought to persuade the unions to work with the Lib Dems on issues like employment rights and the social agenda.

He argued that the "fruits of our cooperation" had been visible with campaigns against low pay for nurses and support for teachers attempting to reduce bureaucracy.

"There's an emerging consensus between us - from Europe to environmental responsibility, from employee rights to worker participation, from public services to the welfare state," Mr Kennedy told the Blackpool audience.

Estelle Morris talked about the importance of education

But while heaping praise on the trades unions, describing them as "healthy for society", he warned against "the language of confrontation".

"Of course we're not going to agree automatically with everything you say - but we will listen," he said.

Euro call

In a reference to Tony Blair's comments earlier this year, Mr Kennedy insisted: "You won't catch Liberal Democrats describing trade unionists as wreckers."

He stressed: "I believe that the momentum of public opinion is swinging towards both of us - Liberal Democrats and trade unionists alike."

Mr Kennedy used his speech to reiterate his party's call for the UK to join the euro, claiming that the country had "fallen woefully behind" its European partners on the standards of hospitals, schools and transport.

He also unveiled his plan to replace National Insurance with an NHS tax, giving people a guarantee that cash raised would be directed towards healthcare.

The proposal, which will be detailed at the Lib Dem conference in Brighton later this month, would take health funding out of general taxation.

Successful speech?

But Mr Kennedy provoked the wrath of some unions by saying he did not believe that everything should be done through the public sector.

Many unions are still deeply worried about the use of the private sector in the public services.

Only a short time before Mr Kennedy took the floor, this anger at the prime minister's policy was demonstrated with a vote objecting to public private partnerships.

However, TUC general secretary John Monks said Mr Kennedy's comments had "hit exactly the right note".

"Trade unions need allies across the political spectrum and there are many issues where unions and Liberal Democrats can work together, particularly our shared support for European values," he said.

"We do not have to agree on everything to have mutual respect for each other."

Critical debate

Mr Kennedy's platform has regularly been described as to the left of the Labour party, although he rejects that tag.

Despite moves by some unions to cut cash donations to Labour and withdraw sponsorship from some Labour MPs, there is no sign they are about to get into bed with the Liberal Democrats.

Mr Kennedy's speech followed Education Secretary Estelle Morris's address to the conference and critical debate on public services in general.

The prime minister clearly failed to win over many of his union critics in Tuesday's keynote speech, in which he repeated his demand for investment in services to go hand-in-hand with reform.

Appeal

Colin Moses, from the Prison Officers' Association, told delegates that the service was "critically over-crowded".

The TUC is calling for all prisons to return to the public sector.

Mr Moses said jails in England and Wales were housing 71,500 prisoners - 9,670 more than they were built for.

"The government needs to positively intervene in our penal system before it is too late," he said.

The debates come on the first anniversary of the 11 September atrocity, which has hung over this conference.

The occasion will be marked here, as elsewhere, with a minute's silence.