The UK's top 350 companies are now in an even worse position to fund schemes based on final salaries, and pay the promised benefit, according to advisers PricewaterhouseCoopers (PwC).
Its pension support index has crashed from 80 out of 100 in March last year to 63, below its previous low of 64 in December 2008.
PwC says nearly one-third of firms have a pension scheme with potential commitments that are dangerously large relative to the size and profitability of their business.
Smaller companies in Scotland face similar pressures, say other advisers, with the latest Bank of England rise in quantitative easing hiking further the projected cost of paying future pensions.
PwC says firms' ability to support final salary pensions "is not much better than it was at the height of the recession, despite pouring billions of pounds into their pension schemes in recent years".
Smaller companies "may need to enter into discussions with their schemes and in some cases consider a restructuring", the firm warns.
Restructuring carries the threat of the scheme being transferred into the Pension Protection Fund, resulting in a loss to all future retirees of at least 10% of their pension payouts.
Martin Potter at Glasgow-based consultants Hymans Robertson, a major adviser to Scottish pension schemes, said that despite efforts in recent years to boost their pension assets, "all the good work has been undone so the deficits are bigger than ever and the cash demands are bigger than ever".
He added: "This is coming as a sucker punch to companies that have been dealing with this for 10 years and not really managing to shrink the deficit.
"The big firms have the infrastructure and resources to manage it over time by throwing more money in, for others battling for survival this is the final straw."
He said the pensions regulator, which normally insisted on a 10-year repayment period for a deficit, would soon be discussing company requests for 15 or 20 year periods as a last resort alternative to restructuring.
Zahir Fazal, a director of Bestrustees, which acts as a trustee to major schemes, said: "From a trustee perspective, it highlights how important it is properly to understand the employer covenant – the employer's ability to support the scheme."
Mr Fazal is chairman of trustees at tiny Scottish cashmere maker Dawson International, which is in discussions with the regulator over its historic deficit.
Dawson currently employs under 200 people, yet is responsible for paying the pensions of 4300 people.
Its £1.8 million payment into the pension scheme last year was three times its underlying profit.
Stuart Faloon, at consultants Mercer, added: "With the increase in current risks, com-panies may have to make higher Pension Protection Fund payments to reflect the increased risk."
l Pensions Minister Steve Webb will today announce plans to make it simple for people to take their work pension (outside final salary schemes) with them from job to job.
Mr Webb said: "At the moment every time someone moves to a new job there is a risk they leave behind a small pension pot which they lose track of.
"We need a system where people build up worthwhile pension pots in one place rather than having lots of small pots all over the place."