The Rail, Maritime and Transport union and the Transport Salaried Staffs' Association have given employers 10 days to meet their demands.

The unions claim many of the schemes for rail workers are in deficit.

They are calling on rail employers to keep their pension schemes open and cap staff contributions.

The unions have warned that a strike this summer will bring the networks to a standstill.

Higher contributions

Before rail privatisation, there was one salary scheme for British Rail workers.

Now there are more than 100 pension arrangements, involving at least 60 companies, including all the train operating companies and engineering firms which maintain the railways.

The unions have previously claimed there is a deficit of up to £600m among pension schemes, and that some workers could see their contributions double without an agreement with employers.

The RMT and TSSA have written to all rail employers, urging them to keep schemes open, cap employee contributions at 10.5% and make other undertakings.

Next week the unions will voice their concerns to transport minister Derek Twigg.

The government has also been asked to push employers into negotiations over the future of pension schemes.