Rail unions have reacted furiously to a warning by the Transport Secretary that changes employers are seeking, which are at the heart of the current train strikes, could be imposed.

Grant Shapps said he would have to enact legislation referred to as a “section 188” to force through some of the measures.

He told Sky News: “What I do know and I can say for sure is if we can’t get this settled in the way that we are proposing, which is, ‘Please put the deal to your membership’, then we will have to move to what is called a section 188; it is a process of actually requiring these changes to go into place so it becomes mandated.

“That is the direction that this is moving in now.”

The Transport Salaried Staffs Association (TSSA), whose members were on strike on Thursday and will walk out again on Saturday, accused the Transport Secretary of “advocating fire-and-rehire” tactics.

The union said Section 188 of the Trade Union and Labour Relations Act is a duty requiring employers to consult trade union representatives, but is not a mechanism for imposing unilateral change.

Such notice for compulsory redundancies has already been issued by Network Rail with its proposal to cut up to 1,900 jobs from the industry, said the TSSA, adding that it was not “reform” but “cuts”.

“Many of the changes being proposed require big changes to people’s contracts of employment including rosters, more night shifts and working practices. These require agreement between unions and the employer. This is another reason we are on strike,” said a spokesman.

“Grant Shapps has not attended any talks with trade unions during the months-long dispute, despite repeated calls for him to come to the table or allow employers to negotiate freely without his and his department’s interference.”

Manuel Cortes, TSSA general secretary, said: “This is yet more desperate stuff from Shapps intended to distract from the real issues in the rail dispute. He’s now actively advocating fire and rehire.

“Grant Shapps is touring TV studios spouting anti-worker nonsense when it’s actually within his gift as Transport Secretary to resolve this dispute.

“At every turn his actions ramp up the dispute and make it harder to get a resolution. It seems clear that he wants negotiations to fail. Any responsible government or employer would understand the devastating impact of their policies on the railway workforce and seek to negotiate with their Unions to find a fair and just way forward.

“Tightening the screw on trade unions won’t resolve the Tory cost-of-living crisis and the desperate calls from people across our country for a pay rise after years of pay freezes.”

Rail, Maritime and Transport (RMT) union general secretary Mick Lynch said: “Mr Shapps has no authority to issue Section 188 notifications as he is not the legal employer but now seems intent on forcing through fire and re-hire on rail workers despite previously claiming that he had nothing to do with negotiations between the employers and the unions.

“Despite his denials Mr Shapps has clearly been dictating how the train companies should conduct negotiations with RMT and now he’s ordering them to fire and re-hire workers.

“The minister also appears to be increasingly desperate and out-of-touch making wild claims about train services between London and Manchester without having a clue what is actually happening.

“Instead of threatening to cut thousands of safety critical jobs, introducing driver-only trains, closing ticket offices, bailing out the private rail companies as well as bringing in more anti-union laws, the Government and the employers should enter meaningful negotiations with RMT.”