Steel unions have begun balloting members on a redundancy package which will pave the way for thousands of job losses in south Wales.

Three unions representing workers – Community, Unite and the GMB – have finalised an agreement with Tata Steel over severance payments and future investment in steelmaking.

In a message to members, the Community union said the agreement was the “best that can be achieved through negotiation” with Tata Steel.

The company has begun restructuring its operations to address losses and reduce its carbon emissions.

Tata Steel closed one blast furnace in Port Talbot in July and plans to close its second at the end of September.

The company has consistently argued that its blast furnace operations were losing £1m a day, and that its commitment to build a £1.25bn electric arc furnace would bring greener steelmaking to south Wales.

Roy Rickhuss, the general secretary of Community, told members that Tata Steel’s proposals would “reduce capacity and slash jobs” and that the union had spent months negotiating the terms of any redundancy.

He said the agreement “includes a number of key elements including significant enhancements to redundancy terms, a skills and retraining scheme, commitments to protect and fully load the downstream operations, and the assurances on future investments”.

The decision to ballot members was the result of a commitment from all three unions to put the decision to a vote by the workers.

More than 2,000 workers have already expressed an interest in taking voluntary redundancy, the majority of whom are based at the UK’s largest steelworks in Port Talbot.

Tata Steel is planning to cut 2,500 posts during the current redundancy period, with a further 300 roles due to close in future.

The company has said that the redundancy terms are its best ever offer to staff.

Employees will receive 2.8 weeks’ salary for every year of service, up to a maximum of 25 years.

They will receive a guaranteed minimum payment of £15,000 and an attendance-related payment of £5,000.

Mr Rickhuss said the imminent closure of Port Talbot’s second blast furnace meant it was “imperative” that workers were balloted now.

He told members that its ballot had opened on Sunday and would close at midday on 16 September.

Workers were also told that an agreement had been reached between the UK government and Tata Steel, which is expected to confirm the £500m grant offered by the previous Conservative government towards the cost of Tata’s new electric arc furnace.

Further details of the government agreement are expected to be announced later in the week.