Controversial moves by the Government to reform strike laws have been roundly condemned by union leaders, one of whom said it "smacks of Germany in the 1930s".
Legislation expected to be published on Wednesday will propose a 50% turnout threshold for industrial action ballots, while in "core" public services such as health, transport, education and the fire service, 40% of those eligible to vote must back action.
Other measures are likely to see the removal of current restrictions on using agency workers to cover for strikers, so that employers will be able to "stick two fingers up" and bring in other staff to break any industrial action, say unions.
The Certification Officer could be given new powers to put more "red tape burdens" on unions, while workers whose unions have a political fund will have to opt into it rather than opting out, which will hit Labour funding.
TUC general secretary Frances O'Grady said: "The Government is determined to strip workers of power at the negotiating table and give bosses the upper hand during disputes.
"Even when ballots succeed in meeting the new thresholds, employers will soon be able to stick two fingers up and bring in agency staff to break strikes.
"This Bill is an affront to fair play. It reads like something straight out of a George Orwell novel. Making it a criminal offence for there to be more than six people on a picket line would be a waste of police time and should worry anyone who cares about civil liberties.
"This legislation is a slippery slope towards worse rights for all."
Mick Whelan, general secretary of the train drivers' union Aslef, said he had "serious" fears over the proposals.
"I think it's shameful that this Tory government is coming after the one group of people – the trade unions – who are able to stand up for ordinary working people as well as the poor and the weak, the oppressed and the dispossessed. They talk about essential services. But all services are essential.
"It smacks of Germany in the 1930s when trade union leaders, and activists, were rounded up, and imprisoned, and, in some cases, executed.
"The Nazis banned unions, and strikes, in 1933, and that is what the Tories are trying to do now. They want to effectively neuter the unions – the only part of civil society now able to fight back – in Britain.
"The Tories are trying to smash the trade unions because they know we are the only thing that stands between them, and the class they represent, and a return to Victorian values – tax cuts for the bankers and the brokers who brought Britain to the brink, for a very few at the top of the pile, and a life on zero hours contracts and the minimum wage for the rest of us.
"It is ironic that this Government, in the year we celebrate the civil rights brought in by the sealing of the Magna Carta 900 years ago, is determined to bring in a law which strikes at the democratic heart of this country."
Unite's leader Len McCluskey said his members had voted to go on strike almost 700 times in the past year, winning virtually every dispute, helped by the union's £32 million strike fund.
He revealed that his union's Rules Conference last week voted to delete the words "so far as may be lawful" before the list of Unite's objectives.
Speaking at the Durham Miners' Gala at the weekend, he said: "Now there will be a fresh Tory attack on trade union rights and democracy.
"The bar for a strike ballot will be raised to a level that hardly any MPs would reach in their own constituencies, by a Government that has refused our requests to use modern, more effective balloting methods (the same balloting methods they use to ballot in their own party).
"Agency labour scabs will be licensed to break strikes, according to the Government's stated plans.
"Pickets can be criminalised, and our Political Fund is under attack from Tories who will continue to take secret donations from hedge fund millionaires.
"Against that background, should the law, when made by an elected parliament rather than a dictatorship, be respected under all circumstances?
"Unite is not going to see itself rendered toothless by passively submitting to unjust laws. If the Tories wish to put trade unionism beyond the law, then they must take the consequences.
"We are ready for the fight, and we will, I believe, find allies throughout society, amongst everyone who cares for freedom and democracy."
A Department for Business, Innovation and Skills official said: "People have the right to know that the services on which they and their families rely will not be disrupted at short notice by strikes supported by a small proportion of union members.
"The ability to strike is important but it is only fair that there should be a balance between the interests of union members and the needs of people who depend on their services."