Tata steelworkers have voted massively to accept reforms to their pensions, clearing the way for investment in the company.

Members of three unions backed changes by around 3-1, giving a mandate to "move forward" following months of uncertainty.

Roy Rickhuss, leader of the Community union, said steelworkers had taken a "tough decision", adding that Tata was now expected to deliver a £1 billion investment plan.

Members of Community voted 72% in favour, on a turnout of 70%, Unite reported a 75% vote in favour on a 69% turnout, while GMB said its members voted yes by 74% in a 51% turnout.

Mr Rickhuss said: "This result provides a mandate from our members to move forward in our discussions with Tata and find a sustainable solution for the British Steel Pension Scheme.

"Steelworkers have taken a tough decision and have shown they are determined to safeguard jobs and secure the long-term future of steelmaking.

"Nobody wanted to be in this situation but, as we have always said, it is vital that we now work together to protect the benefits already accrued and prevent the BSPS from free-falling into the Pension Protection Fund.

"This ballot involved an extremely personal decision for everyone that voted. Whichever way our members cast their votes, we know they will not have taken that decision lightly and everyone's opinions must be respected.

"We now expect Tata to make good on their promises and deliver the investment plan for the whole of their steel business. The UK Government still has an important role to play and we fully expect them to deliver tangible support for steelmaking in the UK."

Unite national officer Tony Brady said: "Steelworkers have made great sacrifices to ensure the UK's world-class steel industry has a future. Those sacrifices must be repaid by Tata Steel honouring its commitments on investment and job security. Nothing less would be a betrayal and add to the deep mistrust that steelworkers now have for the company.

"The UK Government in Westminster must also repay the sacrifices and the commitment shown by steelworkers to their industry by stepping up to support steel and secure its future.

"The UK Government must now work in lockstep with the Welsh Government and put steel at the heart of a manufacturing industrial strategy which ensures UK steel is used in all major infrastructure and defence projects."

Dave Hulse, of the GMB, said: "Now that steelworkers have done their bit, it is time for the Government step up and do theirs.

"Thousands of skilled jobs rely on steelmaking and the industry supports the whole UK manufacturing sector. Instead of insulting steelworkers by classing their industry as a low priority, the Government should set out a strategy for steel that recognises it as a high priority for investment and innovation."

Leaders of the three unions recommended acceptance of the changes as the best that could be achieved through negotiation.

The changes include the introduction of a defined contribution (DC) pension scheme, with maximum employer contributions of 10%, following the closure of the British Steel Pension Scheme (BSPS) to future accrual.

The unions said their independent legal and pension advisers, as well as the BSPS Trustees, advised that the scheme has to close to future accrual because it is heading for the Pension Protection Fund - a lifeboat for failing schemes - and the company into insolvency.

The company intends to close the BSPS to future accrual on March 31 and introduce a defined contribution pension scheme with maximum employer contributions of 10%, based on employee contributions of 6%.

The company's original proposal was to bring in a DC scheme with contributions of 3% from the employer and 3% from the employee.

The BSPS is one of Britain's largest pension schemes, with 130,000 members.

Tata inherited the scheme when it bought Corus, formerly state-owned British Steel, in 2007.

The Indian conglomerate said last year that it would sell its UK business but it has since decided to seek a partner and has been in lengthy talks with German firm ThyssenKrupp.

The pension scheme trustees have warned that the current deficit of more than £400 million is set to rise to between £1 billion and £2 billion at its next actuarial valuation.

A Government spokesman said: "This positive vote is an important step forward for the future of Port Talbot and Tata Steel in the UK and it is now vital that all parties work together to deliver on the agreed proposals.

"It is testament to the commitment of its workforce that they are willing to work so constructively with the owners to secure the future of the plant. The Government will play its role in supporting the steel industry to help deliver a sustainable future."

First Minister of Wales, Carwyn Jones said: "While I appreciate this has been a difficult decision for the trade unions and their members, today's announcement is a significant step forward in securing a sustainable future for Tata's UK business.

"We continue to work closely with Tata to implement our significant financial support package in order to maintain steel jobs and production at all the Tata sites in Wales.

"We also repeat our calls for the UK Government to urgently tackle the UK's high energy costs and continue to push for greater recognition of the steel industry in their new Industrial Strategy."

A Tata Steel spokesman said: "We acknowledge the result of the trade unions' ballot.

"We recognise this has been a difficult decision for employees.

"It shows employees are doing everything they can to develop a sustainable future for the business.

"We will continue to work with the trade unions and other stakeholders to deliver Tata Steel UK's transformation plan and develop a sustainable future for the business."

Shadow steel minister Gill Furniss said: "Steel is a vital foundation industry for the UK.

"That is why it is important that today we have got a way forward for the Port Talbot steelworks, and that is why Labour will keep pressing the Government to give the steel sector the support it deserves.

"That means not marking steel 'low-priority' in the Brexit negotiations and not giving steel just one mention in the whole industrial strategy green paper.

"Actions matter, and this Government has done nothing to show it will actually support the UK steel industry."