The Government will today press ahead with controversial trade union reforms in the face of bitter opposition and warnings of industrial and legal action.
The Trade Union Bill will receive its second reading in the Commons, giving MPs their first chance to debate measures including a new 50% threshold on participation in strike ballots, a fresh clampdown on picketing and changes to the collection of union subscriptions.
Business Secretary Sajid Javid said the reforms will stop the "endless" threat of strike action hanging over "hardworking people."
But unions said the Bill was an attack on civil liberties, and would be strongly resisted.
GMB general secretary Sir Paul Kenny said he would be prepared to go to prison if measures such as fining pickets for not wearing an arm band become law.
TUC general secretary Frances O'Grady will tell the TUC Congress in Brighton that the Bill was the biggest attack on unions in 30 years.
She will say: "Nobody would deny that strikes can be inconvenient. But when it comes to a threat to the fundamental right to strike, the public are with us. Because that's exactly what this government is doing. Attacking the very principle of the right to strike.
"This Bill threatens the basic right to strike. It will allow employers to bus in agency temps to break strikes and will bring in big new restrictions on picketing and protests during a strike, including unions having to tell the police and employers what they will post on Facebook or twitter two weeks in advance."
The Government said that under current laws, industrial action at ongoing disputes on London Underground and First Great Western could carry on for years.
Ministers said there were a number of live mandates for action which were over two years old, including disputes involving teachers and firefighters.
Mr Javid said: "Trade unions play an important role and deserve our respect. But when working people's lives are being disrupted by strike action, it is only fair that this happens as a result of a contemporary mandate that is supported by the majority of trade union members."
Employment minister Nick Boles added: "These modernising reforms will ensure strikes will only happen as a result of a clear, positive and recent decision by those entitled to vote."
The TUC urged MPs to vote against the Bill, saying the public did not support the proposed measures.
Unison leader Dave Prentis warned that his union would withdraw from partnership working in the NHS if the Bill become law, a move he said would affect talks on issues such as equal pay.
"We would then take legal cases rather than reach agreements. There is just no need for this Bill and we will fight it tooth and nail."
Mr Prentis said around a million Unison members paid their union subs through the so-called check-off system, warning that scrapping it could lead to a loss of 30% of his members.
"We would have to manage a smaller union. But we are not sitting back - we will drastically increase the number of full-time officials dealing with membership.
"The Bill would have an incredibly bad impact on industrial relations in this country and takes away the ability of workers to have a voice. It will bring in a police state. We would also not be able to reach an agreement with employers to collect subs from wages - for which we pay them."
Sir Paul hit out at provisions in the Bill on picketing, including fines for those not wearing an official arm band, as well as pickets having to give their names to police.
If they are criminalising peaceful picketing to the point where someone not wearing an arm band gets fined £20,000, then I will turn up without an arm band. If someone has to go to prison, I would go first. It would not worry me in the slightest."
Mark Serwotka, leader of the Public and Commercial Services union, said the Bill offered the best reason for mass demonstrations on picket lines.
PCS members at the National Gallery are on all-out strike over privatisation and the dismissal of a union rep and Mr Serwotka warned that thousands of people will turn up at their picket line if the Bill becomes law.
"I think people will refuse to abide by the law," he said.
Unison's Dave Prentis added: "The Government should be concentrating on the real issues the country faces. But instead it is wasting time trying to prevent ordinary women and men from standing up for themselves, and denying them the right to go on strike, when every other attempt to solve a problem at work has failed.
"When unions and the women and men who belong to them win a pay rise, more flexible hours or safer working conditions, all their colleagues benefit. If this vindictive Bill becomes law, it won't just be unions and their members who lose out, it will be all employees, with bad bosses the only winners."
Labour MP John McDonnell, a close ally of new party leader Jeremy Corbyn, told trade unionists last night that Labour will unanimously oppose the Bill.
He also pledged to support demonstrations and protests, saying to huge applause: "We will support all demonstrations in Parliament or on the picket line. We will be with you at every stage.
"It is not often you have heard that from a Labour MP but you are hearing it now."
Mr McDonnell accused the Government of conducting a "scorched earth "policy against unions. He accused the Conservatives of trying to remove opposition to spending cuts by "destroying " unions.
"This is part of the policy of the austerity programme - remove resistance to make it easier to cut services and jobs and undermine the welfare state."
Mr McDonnell said the Government will follow the second reading of the Bill by having brief debate in the Commons on Tuesday on cuts to working tax credits.
"We need determination and courage to stand up to this abuse. "
Unite leader Len McCluskey predicted that the divisive nature of the Bill would be its downfall. He told the fringe meeting that he dealt with chief executives of every major company and none of them wanted the proposed legislation.
A Business Department spokesman said: "Trade unions can play a constructive role in maintaining positive industrial relations and this Bill will not stop them from partnership working with the public sector on important issues such as training and equal pay.
"The Government supports the ability to strike but there must be a clear mandate from members to protect the interests of working people who need to know that they can get to work or take their children to school.
"There is nothing in the Bill which goes beyond what is already required in the Code of Practice on Picketing and has been followed without difficulty by the majority of unions for decades. Financial penalties range from a minimum of £200 to a maximum of £20,000 and would be levied on a union not on an individual member.
"The outdated practice of state-run trade union subscriptions is to be ended removing the taxpayer-funded administrative burden on employers. There is no reason why a trade union with a good relationship with their members would lose out by asking them to pay by direct debit."