Liz Truss has pledged to do “everything in her power” to ensure “militant action” from trade unions can no longer “paralyse” the economy if she wins the Tory leadership contest.

The Foreign Secretary announced a series of measures aimed at preventing trade unions from causing disruption on strategic rail routes and other national services.

If she becomes prime minister at the beginning of September, Ms Truss said her government would introduce legislation in the first 30 days of Parliament to guarantee a minimum level of service on vital national infrastructure.

Tailored minimum thresholds, including staffing levels, would be determined with each industry.

She would also ensure strike action has significant support from union members by raising the minimum threshold for voting in favour of strike action from 40% to 50%.

The minimum notice period for strike action would be raised from two weeks to four weeks, and a cooling-off period would be implemented so that unions can no longer strike as many times as they like in the six-month period after a ballot.

Ms Truss would also put an end to members receiving tax-free payments from trade unions on the days they are on strike.

She said: “We need tough and decisive action to limit trade unions’ ability to paralyse our economy.

“I will do everything in my power to make sure that militant action from trade unions can no longer cripple the vital services that hard-working people rely on.”

A campaign spokesperson said: “Liz is determined to stand up for people who work hard and do the right thing.

“For too long, trade unionists have been able to hold the country to ransom with threat of industrial action.

“The steps she has announced today will finally allow the government to take back control from trade union barons and deliver the economic growth we need to put money back in hard-working families’ pockets.”

Ms Truss’s pledge comes as rail services are set to be severely disrupted on Wednesday, with thousands of workers staging a fresh strike in a bitter dispute over jobs, pay and conditions.

Members of the Rail, Maritime and Transport union (RMT) at Network Rail and 14 train operators will walk out, crippling services across the UK.

Angela Rayner, Labour deputy leader and shadow secretary of state for the future of work, said: “Liz Truss is looking to blame anyone and everyone else other than herself for the mess the Conservatives have made of the last 12 years.

“Her latest Tory fantasy is dangerously out of touch with reality and ignores the stubborn fact that she has sat around the Cabinet table for nearly a decade of pitifully low wage growth, crumbling public services and sleaze at the heart of Government.

“As we saw with the Government’s plans to break strikes with agency workers, these plans are unworkable, will only erode working people’s rights further and inflame industrial relations at a critical time.”

TUC general secretary Frances O’Grady said of the proposals: “The right to strike is an important British freedom.

“Threatening the right to strike means working people lose the power to bargain for better pay and conditions.

“Instead of taking potshots at working people and their unions, the candidates should come up with plans to get wages rising again. That’s how to deal with the cost-of-living emergency.”

RMT general secretary Mick Lynch said: “The proposals by Liz Truss amount to the biggest attack on trade union and civil rights since labour unions were legalised in 1871.

“Truss is proposing to make effective trade unionism illegal in Britain and to rob working people of a key democratic right.

“If these proposals become law, there will be the biggest resistance mounted by the entire trade union movement, rivalling the General Strike of 1926, the Suffragettes and Chartism.”