Royal Mail yesterday confirmed it would close its final-salary pension scheme to new members - within days.

Action has been taken on the corporate pension scheme, which has 45,000 members, after it incurred a £5bn deficit.

The Communications Workers Union is balloting all Royal Mail employees on rejection of the plans. It said the ballot result will be announced on Tuesday when the union will also be meeting to consider its next step.

Royal Mail said longer life expectancy and a sharp rise in pension costs has forced the state-owned group, which lost its 350-year monopoly on postal services in 2006, to close the scheme, which was bitterly opposed by workers.

From April 1, the pension scheme will move to benefits based on the average earned by employees during their career, rather than their final salary. Royal Mail will launch a new defined contribution salary scheme in April 2009.

Postal workers will continue to take their pension from the age of 60 until April 1, 2010, when the retirement age will rise to 65. After that, it will be possible for staff to draw a pension at the age of 60 on benefits accrued before April 1, 2010, while continuing to work until they reach the maximum level of benefits.

Jon Millidge, Royal Mail's Interim Group HR director, said: "Changes are unavoidable given increasing long-evity and the higher costs of providing the current pension plan - but Royal Mail remains committed to continue offering postmen and women the best pensions the company can afford."

The latest financial figures show Royal Mail's profit fell by 34% to £233m.