The new minimum service level regulations will also make sure "certain priority routes can remain open" - though it is not yet clear which journeys will be covered.

Other rules will be introduced for border security staff and ambulance workers, in plans Prime Minister Rishi Sunak says will "stop unions de-railing Christmas for millions of people".

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The details follow on from the government's Strikes (Minimum Service Levels) Act that it passed in January, giving ministers the power to set minimum service levels across multiple sectors.

The legislation caused an uproar from unions, who have again slammed the government for its latest move, calling it "unworkable" and "undemocratic".

The TUC's general secretary, Paul Nowak, said: "These anti-strike laws won't work. The crisis in our public services is of the government's own making.

"Rather than engaging constructively with unions, they are attacking the right to strike. And they are punishing paramedics and rail staff for daring to stand up for decent pay and better services."

Labour's deputy leader, Angela Rayner, also claimed the government was "getting their excuses in early for Christmas", adding: "Rishi Sunak is offering another sticking plaster to distract from the Conservatives' track record of failure.

"We all want minimum standards of service and staffing but it's Tory ministers who are consistently failing to provide them."

But Mr Sunak said it was the "right long-term decision... to keep people safe and continue delivering the vital public services that hard-working people rely on".

Under the new law, employers will be able to issue notices to people "who are reasonably required to work to ensure minimum service levels are met", the government said.

It will also make unions "take reasonable steps and ensure their members who are identified with a work notice comply" - with the statutory guidance set out by the Department for Business and Trade following a consultation.

If unions fail to do this, they can be sued, with the maximum fine for unlawful strike action now sitting at £1m.

"We are doing everything in our power to stop unions de-railing Christmas for millions of people," said Mr Sunak.

"This legislation will ensure more people will be able to travel to see their friends and family and get the emergency care they need.

"We cannot go on relying on short term fixes - including calling on our Armed Forces or civil servants - to mitigate the disruption caused by strike action.

"That's why we're taking the right long-term decision to bring in minimum service levels, in line with other countries, to keep people safe and continue delivering the vital public services that hard-working people rely on."

The rules for border security will apply to both the Border Force and selected HM Passport Office staff, and state that services "should be provided at a level that means that they are no less effective than if a strike were not taking place", as well as ensuring all ports and airports remain open on a strike.

For ambulance workers, the legislation will only impact England, and will "ensure that cases that are life-threatening, or where there is no reasonable clinical alternative to an ambulance response, are responded to".

The three areas have been chosen following government consultations to establish what they think are the correct minimum service levels to introduce following a raft of strikes that have dominated the past year.

But the Department of Health and Social Care is still carrying out on "expanding the scope of minimum service levels to cover other urgent and emergency hospital-based services", which could include nurses and doctors.

Unison - which represents ambulance workers, as well as other healthcare professionals - called the legislation a "pointless move [that] won't solve a single problem in the NHS".

The union's head of health, Sara Gorton, added: "Measures are already in place to protect patients during action. Sacking ambulance workers on strike won't get the millions awaiting hospital treatment any closer to the top of the list.

"It's just a desperate attempt to deflect attention from the government's appalling record on the NHS.

"The public wants ministers to cut waiting times, shorten delays and attract more staff to the NHS. Not make an already dire situation significantly worse."

The Department for Education has already committed to introducing minimum service into schools and colleges, though at the moment it will be on a voluntary basis with agreement from unions.

However, ministers will launch their own consultation if an agreement can't be reached.

The Department for Business and Trade is also launching a consultation on removing regulations that prevent agency workers being supplied to cover striking employees, with a promise to publish its findings "in due course".

The TUC's Mr Nowak said unions would continue to fight back against the "spiteful legislation", adding: "We won't stop until it is repealed."

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