Directors of Britain's top companies were accused yesterday of insulating themselves from the country's pensions crisis after figures revealed they had amassed pensions worth 

Unions accused directors of an "upstairs-downstairs" policy that protected directors while forcing workers to accept huge cuts to retirement incomes.

The TUC's analysis of boardroom pensions shows the average executive of a FTSE 100 company can retire at 60 on a final salary pension worth nearly £3m. The largest director's pension in each company is on average nearly £5m, more than 40 times most staff pensions. The BP boss Lord Browne heads the list of top earners with a package worth almost £20m. When he retires next year his annual retirement income will be in excess of £1m.

Over the past decade, two-thirds of FTSE 100 companies have closed their final salary occupational schemes to new members. Some companies, including Rentokil Initial, have gone further and forced existing staff to accept cheaper pension arrangements. By contrast, the report says that in 80% of companies, board directors maintain the right to join a more generous final salary scheme.

Directors are granted further benefits including early retirement and the accelerated accrual of pension benefits. Lord Browne, like most FTSE 100 directors, accrues pension rights at twice the rate allowed for workers. One-off payments are a popular way of boosting directors' pensions. One employer paid more than £1m into a director's money purchase (defined contribution) pension last year, and the five biggest payouts to this type of pension top £300,000 annually.

A report by Labour Research says directors at Astra Zeneca, Standard Chartered and HBOS can retire at 55 with no reduction in their final salary pension. Christopher Keljik retired from Standard Chartered's board in May 2005 aged 56 on a pension worth £306,000 a year.

In response, the CBI said directors brought extra value to their companies and deserved their pension payments.

A CBI spokesman, John Cridland, said long-serving directors, like long-serving employees, are more typically in higher-paying defined benefit schemes. "The TUC screams blue murder if ever it is suggested that employees' schemes should be changed retrospectively. Surely it applies the same principle to long-serving senior executives?"

The TUC general secretary, Brendan Barber, said the CBI's comments failed to address demands for fairness and clarity. "Britain's boardrooms and business lobby groups have failed to tackle upstairs-downstairs-style company pensions. If bosses were in the same scheme on the same terms as staff, they would still build up massive pensions compared to employees but they would be fairer. It would also help reduce their company pension deficits. Investors should demand uniform and open reporting of staff and executive pensions from companies."

The figures are expected to stir emotions at the Labour and TUC conferences. They also come at an awkward time for the government, which is due to publish details of its planned reforms for pensions by the end of the year.