Workers at Tata Steel have voted by almost 9-1 to go on strike in a row over pensions, threatening the first national walkout in the industry for more than 30 years.
Members of the Community union backed strikes by 88% and other forms of action by 96% in a turnout of 76% - all well above new thresholds for union ballots being planned by the Government.
Unions are protesting against plans to close the British Steel Pension Scheme to future accrual, which they say could see workers retiring at 65 instead of 60.
The company has warned that its pension scheme is heading for a huge shortfall of £2 billion .
Roy Rickhuss, general secretary of Community, said: "We stand on the brink of the first national strike in the steel industry for over 30 years.
"This is not where we wanted to be but Tata now has an opportunity to end this dispute by removing the threat of scheme closure and discussing alternative measures to resolve the challenges faced by the scheme, something the unions have been prepared to do since November last year.
"Throughout those discussions, the company said it needed to address a deficit of just under £1 billion and the unions were prepared to look at measures that would have wiped that out, without closing the scheme.
"Community's members at Tata Steel have now spoken loud and clear. Steelworkers are determined to stand up to Tata. They have not been fooled by the company's propaganda. They have voted overwhelmingly for their pensions, their families and their futures. The company should heed this message and return to meaningful discussions with the unions in line with Tata's values of responsibility and integrity.
"Through Community's network of Tata Steel union representatives, we will begin to consult our members on the kind of action that they want to take. Any action we do take will aim to cause maximum disruption to the company with minimum pain for our members. We hope this can be avoided if Tata return to the negotiating table with new proposals."
Members of Community's executive will meet on Monday to discuss the next move.
Before the ballot result was announced, chief executive of Tata Steel's European operations Karl Koehler sent an open letter to workers urging them not to support industrial action.
"Our actions have been aimed at developing an affordable and sustainable pension scheme through changes that are fair and balanced for all those who work for us, from the younger generation to our longer-serving team members who have given most of their lives to the UK steel industry.
"The past few years have seen the UK, and most of the world, go through the worst financial crisis for generations. One of the consequences has been record low interest rates. And like savings in the bank, our pension scheme's assets have not been growing fast enough to keep up with increases in the expected cost of providing benefits.
"The result has been a huge shortfall of up to £2 billion, which is clearly not sustainable," said the letter.
"The changes we've proposed to our UK pension scheme will help protect the benefits colleagues have already earned. They will also, crucially, ensure a good pension for our people in the future which is both affordable and sustainable.
"Of course we looked at keeping the final salary scheme running, a scheme which by today's standards is a very generous package. Indeed, we initially proposed reasonable measures to the unions that would have addressed the huge shortfall while also being fair and balanced to all colleagues across the age range. Sadly, this was rejected by the trade unions.
"The unions continue to insist on keeping unaffordable early retirement enhancements in the pension scheme which would favour our older colleagues - but would be to the detriment of younger members of the team. I believe the unions' proposals would be unfair and unbalanced.
"Because of this, we have been unable to agree on a way forward. But we have always said we are open to talks and further negotiations with the unions and that continues to be the case."
More than 6,000 Community members were balloted.
The GMB said its members at Tata Steel had also voted in favour of strikes.
National officer Dave Hulse said: "GMB members have sent a clear message to the company that they will not sit back and let them take away their hard earned pensions.
"The company need to take the threat away of closing the final salary scheme and come back around the table to have meaningful negotiations before this is taken out of their hands. Our members will take whatever action is needed to keep the scheme open.
"We have lost faith in the company and its leadership and believe the company are putting the business at serious risk. They now have an opportunity of putting things right by sitting down with the steel committee and having meaningful discussions that are acceptable to all."