The Conservative government is planning to make "significant changes" to the way unions can call a strike. What do we know about the planned changes so far.
What is being proposed?
According to the Department for Business the changes to the strike ballot rules are likely to include:
- At least 50% of members entitled to vote must do so for ballots on industrial action to be valid. Currently balloting rules do not require any specific level of participation by union members.
- 40% of those eligible to vote must back action for strikes in core public services (Health, Education, Transport & Fire Services). Ballots currently require a simple majority to back action.
- Removal of restrictions on using temporary workers to cover for striking staff. A ban has been in place since 1973.
- Tightening rules on ballot mandates. This would prevent unions undertaking action based on historic strike ballots.
- Unions must appoint a picketing supervisor to help provide protection for non-striking workers. Employers will be able to seek injunctions or damages from unions that break these new rules.
- Increasing to 14 days from seven days the notice a union must provide workers ahead of a strike.
How much harder does it make a strike?
The TUC says that the new thresholds will make legal strikes close to impossible.
"Union negotiators will be left with no more power than Oliver Twist when he asked for more," a spokesperson said.
It will be a particular problem in the public sector where postal ballots of large workforces rarely achieve high turnouts.
Even if unions achieve the 50% turnout, they then need 40% of those eligible to vote to back the action. That amounts to an 80% vote in favour of strikes - far higher than that needed to win a general election.
The major public sector strikes on pay and pension reform during the last parliament would not have been possible based on the new thresholds.
The PCS Union, which frequently calls strikes amongst its members in the civil service, has never achieved a 50% turnout on a national ballot.
But the Business Secretary Sajid Javid said: "This is a One Nation Government acting in the interests of the whole country and these reforms will stop the 'endless' threat of strike action hanging over hardworking people."
"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 union members."
How does it compare with other countries?
Trade unions say the UK already has some of the toughest strike laws in the world.
Some European countries don't require unions to hold a strike ballot to call industrial action. Of those that do, few specify a turnout threshold. Most require a simple majority to back strike action.
In Germany, the majority needs to be above 75%, says Guglielmo Meardi, professor of industrial relations at Warwick Business School. But, in common with some other European nations, ballots are held in workplaces rather than by post, which tends to mean higher turnouts.
In any case, there are more "channels of communication" through which an agreement can be made before a strike is deemed necessary.
In countries such as France and Germany unions are more involved in decisions. The use of work councils, where both unions and employers are represented, means workers tend to have more of a say in negotiating pay and working conditions. This means that the industrial relations climate tends to be less confrontational. But major strikes - like the current dispute by German pilots - are not uncommon.
Countries such as France and Italy, which have previously sought to toughen up rules on strikes, have been more surgical in applying new regulations to areas which are particularly disruptive to the public - such as education and transport, says Prof Meardi. And in those countries, union meetings with ministers are more common.
"If new regulations are introduced in a unilateral way, you may even radicalise the unions," he adds, leading to more informal disruptions such as refusal to do overtime.
What else is in the bill?
- Trade union members will need to "actively opt-in to their union's political fund" for donations to political parties by writing to the union. Many unions donate to the Labour party.
- There are likely to be new restrictions on how much time public sector employees can spend on union work.
- Employers facing industrial action "can directly hire workers to provide industrial action cover, or contract out the work to a service provider," according to one policy document. Effectively, a company or department can temporarily replace striking workers with temps.
What do the trade unions say?
Unions regard the UK government's move as an attack on the fundamental human right of workers to withdraw their labour.
They say that the thresholds do not apply to any other elections, like those for Police Commissioners and the Mayor of London. And they think that if the government were serious about increasing participation in voting it would allow electronic balloting or secret balloting in the workplace.
The TUC warns that turnout thresholds can make an abstention a better way of objecting to a strike than a no vote. They say that it cannot be right to encourage people not to participate in a ballot.
"This bill threatens the basic right to strike. It'll 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," TUC General Secretary Frances O'Grady said.
The proposed ability to use temporary workers could be what hits unions hardest, says Steve Coulter, who teaches political economy at the London School of Economics.
While skilled jobs will be more resilient, low-skilled cleaning workers, for example, may struggle to make as much of an impact under the new rules, he says.
"That really undercuts the power of the strike," he adds.