A train at steelworks in Port Talbot, the Welsh town where Tata Steel employs almost 4,000 © Bloomberg

Trade unions demanded further assurances on jobs, investment and future production in the UK after the European steel merger agreement between India’s Tata Steel and Germany’s ThyssenKrupp.

Tata, which has entered into a memorandum of understanding with a view to merging its European steel business, employs 6,000 people in Wales, including almost 4,000 at Port Talbot.

“The devil will be in the detail,” said Roy Rickhuss, general secretary of the Community union.

“As a priority, we will be pressing Tata to demonstrate their long-term commitment to steelmaking in the UK by confirming they will invest in the reline of Port Talbot’s Blast Furnace No.5.”

In addition to the large Port Talbot site, one of only two integrated steelworks in the UK that produce the metal from raw materials, Tata also runs a number of smaller plants in Britain.

The new merger will mean a review of support functions such as IT and human resources, but most of those are no longer in the UK. Unions have been told that there will be no asset closures or cuts in production capacity in Britain.

Greg Clark, the UK business secretary, said ministers had been working behind the scenes with the unions to secure a sustainable future for the business.

“Today’s agreement between Tata Steel and ThyssenKrupp is an important next step in establishing their shared ambition for Port Talbot as a world-class steel manufacturer, with a focus on quality, technology and innovation,” he said.

Mr Rickhuss also demanded reassurances that the ThyssenKrupp pension liabilities would be ringfenced so that British steelworkers did not end up funding German pensions. Tata cleared an important hurdle by agreeing with UK regulators to hive off a pension scheme for its British business last month.

Its workers had earlier this year voted to accept the fund’s closure in exchange for a rescue package.

The Community leader said he recognised the industrial logic of the partnership, but said he would seek an urgent meeting with Tata to discuss its intentions.

Tata Steel’s original decision to close or sell the business in the spring of 2016 plunged Downing Street into panic. David Cameron, the then prime minister, was fearful that he would be blamed for the decline of one of Britain’s great historic industries under his watch at Number 10.

Ministers spent weeks trying to come up with radical solutions to save the business, including a rewriting of pension law, for the steel industry alone, to make it more appetising to possible bidders. By the time of the EU referendum in late June 2016, the management had been persuaded to abandon the fire sale.

Stephen Kinnock, the Labour MP for Aberavon, which includes Port Talbot, said he welcomed the agreement “in principle” because it offered a clear long-term commitment to the future of Port Talbot.

Mr Kinnock said the works had already been through an “incredibly tough and painful restructuring” in recent years.

“These are early days and it is also important to strike a note of caution. In February Tata Steel committed to investing £1bn, to maintaining the blast furnaces, and to averting compulsory early redundancies,” he said.

“Those commitments must be honoured, and I will be seeking assurances from the company that they are in no way affected by today’s news,” he added. “True to form, government ministers [are] still all talk and warm words, but we shall continue to press them for action.”

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