Unfortunately, for lovers of open-and-shut cases, both sides have a point in the dispute over pensions at Grangemouth.

Unions, led by Unite, are in uproar over plans by Ineos, the owner of the former BP site, to close the company's final salary pension scheme to new members. These prized schemes deliver a payout based on the salary of an employee at the time that they retire.

Under proposals being tabled by Ineos, the existing 1,400 staff at Grangemouth would retain their final salary scheme, but any new employees would be offered a “money purchase” alternative, for which the payout at retirement is linked to the fortunes of the stock market.

Ineos is also asking staff to contribute up to 6 per cent of their salary to ensure that the scheme is workable over the long term. Somewhat extraordinarily, until now employees have not had to make contributions.

It is easy to see Ineos's position. The company, which is trying to secure a £750million investment in Grangemouth and to guarantee 650 jobs, spends more than a quarter of its salary bill on providing pension benefits to its workforce.

A qualified technician at Grangemouth can earn £50,000 or £60,000 a year, including bonuses and overtime. Money purchase schemes are undeniably cheaper and transfer much of the risk associated with the pension from the company to the worker.

With the workforce increasingly living longer, the cost of retirement benefits is going just one way: up. Hen's teeth are more common than a non-contributory pension scheme.

Following a consultation period that was due to end in June, Ineos has promised to make “no major changes” to pension provision until 2009 and to phase in any new measures.

Ineos is by no means alone; it is simply joining the relentless move by corporate Britain to jettison its previous rock-solid guarantee to provide a secure income at retirement.

According to the latest annual survey from the National Association of Pension Funds, only 31 of the blue-chip FTSE 100 companies in Britain operate final salary schemes that are open to new members. To do so, particularly at a time of looming scheme deficits, can put the future of an entire corporation at risk, according to the experts.

Unite's position appears equally reasonable. For a traditionally blue-collar workforce, many of which tend to stay in the same job at an uninflated pay rate for a lifetime, a generous retirement scheme is an expected part of employment benefits.

When a company such as this institutes changes to the pension scheme, unions equate it with a real-term cut in salaries. Ineos is a profitable company and the pension scheme is affordable and not operating a deficit. If BP can operate a non-contributory final salary scheme, why can't Ineos?

Moreover, unions are rightly worried about the creep effect — once the unassailability of the pension scheme is removed, it will not be long before further rights are eroded.

Whether you believe that unions should wake up and smell the coffee over changes in retirement provision or that it's time to end the pensions rot, one thing seems almost certain. By retaining a generous scheme for existing workers while denying new staff the same benefits, Ineos is likely to create a two-tier workforce. At the very least, the gulf that will separate new and existing employees in terms of benefits will create resentment. And, as the band of final salary scheme holders dwindles, the days of its existence will be numbered.

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