“INSULTING” Tory proposals to let bosses use agency workers to break strikes would be “reckless and endanger public safety,” unions warned today.

The furious backlash came after Transport Secretary Grant Shapps said new legislation was needed to “prevent disruption and stop the country being held to ransom.”

The Welwyn Hatfield MP told the Sunday Telegraph newspaper that the potential change might be introduced via secondary legislation, which can be signed off by ministers “very fast.”

The government has been stepping up its anti-union rhetoric in recent days following rail union RMT’s announcement of three national strike days later this month — the largest to hit the rail network since 1989.

The industrial action, set to involve more than 50,000 workers at Network Rail and 13 train operating companies, is about fighting deteriorating real-terms pay, working conditions and cuts to thousands of safety-critical jobs, the union has stressed.

Referring to the strike, which was backed by 89 per cent of RMT members on a 71 per cent turnout, Mr Shapps said that “further measures certainly would come in if it can’t be resolved.”

He has already threatened to introduce minimum service levels requirements on railways which would make industrial action illegal unless a certain number of staff are working. 

RMT general secretary Mick Lynch said: “Grant Shapps needs to stop smearing the RMT and unshackle the rail operating companies so they can come to a negotiated settlement that can end this dispute.

“Railway workers voted overwhelmingly for strike — it is insulting to them to suggest they do not understand the issues that affect their daily lives or cannot make a democratic decision by themselves.

“We already have the most restrictive anti-democratic trade union laws in western Europe and if the government attempts to reduce our rights further, the trade union movement will mount the fiercest resistance possible.”

Mick Whelan, general secretary of train drivers’ union Aslef, called the idea “impractical” and asked where thousands of agency workers would come from.

He told the BBC: “You can’t just ship in a load of signallers and train drivers.

“If they are not working for the railway now they are either not medically fit, have been dismissed or don’t want to do it any more.”

Many of the union’s train and tram drivers are set to hold their own strikes at three different rail companies over the next month after years of declining take-home pay. 

TUC deputy general secretary Paul Nowak accused ministers of being “desperate to distract from their own numerous failings by picking a fight with unions.”

He added: “Allowing agency staff to replace striking workers would undermine the right to strike and be extremely reckless.

“[It] would create genuine safety risks for the public, worsen disputes and poison industrial relations.

“Having repeatedly promised a high-wage economy, ministers now seem determined to reduce workers’ bargaining power and to make it harder for working people to win fair pay and conditions.”

The plan is mainly motivated by Prime Minister Boris Johnson’s desire to “throw red meat to his rebellious backbenchers to try to shore up his position” following the “partygate” scandal, Mr Nowak argued.

Unison head Christina McAnea said the government’s focus should be “on a plan to help the country through the cost-of-living crisis, not engineering a distracting spat with unions.

“Using agency workers isn’t safe and only serves to sour relations between employers and their employees.”

Labour also slammed the “unsafe” plan, with shadow chancellor Rachel Reeves telling the BBC’s Sunday Morning programme that government officials were “acting like arsonists rather than firefighters.”