GMB leader Paul Kenny urged Labour to take on rogue bosses today in a speech to the party's conference.
He urged delegates to "condemn the attacks on workers' rights by the Tory-led coalition" and its plans to make it easier for firms to fire people.
Mr Kenny said: "Labour in government has often been scared of tackling rogue employers. But it needs to have a fundamental role in protecting the many against the few.
"Investing in multinationals is not a legacy to be proud of. Labour needs to stand up for the victims of blacklisting by giving no contracts to companies that blacklist."
He praised a report on blacklisting by construction union Ucatt and said workers should not be embarrassed by standing up for their human rights.
Ucatt's Terry Renshaw said: "Blacklisting is nasty, deceitful and vindictive.
"But unfortunately this disgusting practice is still in full swing across Britain.
"Regulations are too weak to deter blacklisters."
Yet Labour MP Dave Anderson said it was not just the Tories, but "the 50-odd yellow-bellied Liberal Democrat MPs who come to Parliament day after day to vote against rights for working people."
Unite assistant general secretary Gail Cartmail said: "Labour should beef up the law on blacklisting to make sure workers are properly protected so they can speak out about health and safety concerns without fear of losing their jobs."
Conference called on Labour "to set up a commission to create fair rights for millions of working people whose hard won rights are being dismantled under the guise of 'flexibility'."
Delegates also backed a motion calling for an economic alternative to cuts and austerity that rejects government proposals for regional pay and calls on Labour to campaign for a living wage.
Unison general secretary Dave Prentis said: "Ordinary workers who have nothing to do with the financial crisis are now paying the price.
"The party needs to stand up for fair pay and fight against market madness."
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