Britain's biggest union threw down the gauntlet to the Con-Dem government yesterday with a pledge to resist attacks on its members.

The defiant stand was declared at Unite's industrial sector conference in Brighton.

And it drew support from the public sector with calls to "resist the onslaught and work together" against rogue bosses and the government.

Unite general secretary Len McCluskey said the trade union movement was experiencing "the most vicious attacks since the 1970s."

He told 1,300 delegates that there would be "no retreat" from confronting abusive employers.

Unite has been subjected to scurrilous attacks by Tory mouthpiece the Daily Mail after peaceful protests were mounted against bosses of the Grangemouth refinery in Scotland.

Accusing the media of a "witch-hunt" he said: "We are facing unscrupulous smears from both media and politicians."

But he said the attacks showed that Unite's resistance is working.

"This shows one thing above all," he said. "Unite is making a difference. We have served notice on the Establishment that fighting trade unionism is back - and the elite don't like it."

He accused the media and Tories of using Unite as a "proxy for smearing the Labour Party and Ed Miliband."

Public and Commercial Services Union general secretary Mark Serwotka - whose union is in merger talks with Unite - called for united resistance against the Tories and their Lib Dem co-conspirators.

"There is no doubt that the Tories in this government want to finish off what Thatcher started because they represent millions of people and remain the only real opposition to political and industrial abuse," he said.

"We must resist this onslaught and work together, including joint strikes, to defend our members, our communities and public services."

And public service union Unison general secretary Dave Prentis said the coalition was intent on destroying the trade union movement.

"Wholesale destruction of our public services and the people who work in them will fulfil their agenda of cutting unions out of the workplace," he said.

"Handing over huge swathes of our health and public services to their friends in big business is one clear example of this end plan.

"The Lib Dems have colluded in the most shocking attacks on those who can least defend themselves.

"Our union has always stood up for the weak, the sick and the vulnerable.

"If you silence the union's voice you silence the people who most need a voice.

"We are the ones who stand in the way of the Tories' objective."

Unite, Unison and PCS are among 15 signatories to a Manifesto for Collective Bargaining drawn up by the progressive Institute of Employment Rights.

The proposals include establishment of a Ministry of Labour to give workers a voice in Parliament to "balance out" corporate interests.