Labour politicians have urged Tata Steel to avoid taking irreversible action before next week’s general election after the Indian company announced it was bringing forward plans to shut down blast furnaces at its Port Talbot plant because of industrial action.

Britain’s biggest steel producer has told workers at the South Wales plant that it could halt operations there earlier than planned because of a looming strike by members of the Unite union.

The company had been preparing to shut one of the furnaces by the end of June and the second by September as part of a government-funded plan to shift production to a less carbon-intensive electric arc furnace.

Unite called the strike in protest at the plans which it says will result in the loss of thousands of jobs.

Workers have now been told that because of the strike from July 8 Tata has been “left with no alternative but to take preparatory steps to cease operations on both blast furnaces and safely isolate them no later than July 7”.

The move was condemned by Unite and prompted Labour politicians to call on Tata to delay.

In a joint statement, Stephen Kinnock, Labour’s parliamentary candidate for Aberafan Maesteg, and David Rees, Labour’s member of the Senedd for Aberavon, said: “Everybody recognises that the number one priority in these negotiations has to be the safety and security of steelworkers and the plant.”

But they added: “Tata wouldn’t be in this position of facing strike action had it not chosen to press ahead at breakneck speed with the closures of the blast furnaces.

“We have been consistently clear throughout this process that Tata should avoid taking any action that cannot be reversed before waiting to see the result of the general election, given the very real prospect of sitting down with an incoming Labour government to discuss its promised £2.5 billion steel renewal fund.”

Labour has promised to negotiate a better deal for the industry if it comes to power and has previously urged Tata to reconsider a compromise plan supported by the Community and GMB unions to retain one of the blast furnaces, which has a lifespan that could run into the early 2030s, until the electric arc furnace is operational.

The proposal is estimated to cost the taxpayer more than the £500 million offered by the Conservative government and has been rejected by Tata, which plans to invest £750 million to decarbonise its UK operations as part of the deal with ministers.

Tata, which has launched legal action against Unite’s ballot, said having to “pause or stop heavy end operations, including both blast furnaces … is not a decision we would take lightly and we recognise that it would prove extremely costly and disruptive throughout the supply chain, but the safety of people on or around our sites will always take priority over everything else”.

Sharon Graham, general secretary of Unite, said: “Tata putting out a statement to shut or pause its blast furnaces three months earlier than they intended to is the latest in a long line of threats that won’t deter us. We call on the real decision makers in Mumbai to take hold of this dispute.”