Three million workers with final salary pensions have 50 per cent chance of losing up to fifth of their income because their employers have made unaffordable promises, a report has warned.

A growing number of employers who have offered staff so-called "final salary" pension schemes are coming under extreme pressure to meet their obligations, the Pensions and Lifetime Savings Association said.

This is down to a range of factors including people living longer than expected, making guaranteed pensions more expensive to provide.

Companies who find they cannot afford to pay the pensions they have promised staff will have their pension schemes rescued by a lifeboat service called the Pension Protection Fund.

Workers whose pensions are taken over by the fund are still paid a pension, however the amount they receive can be up to a fifth lower than what they were originally promised.