Strike action at some of England's national museums looks likely if staff reject pay deals currently on the table.

Some 88 per cent of staff at the four sites run by the National Museum of Science and Industry (NMSI) - the Science Museum, London, National Media Museum in Bradford, National Railway Museum, York and Science Museum, Swindon - voted to reject the pay offer as Museums Journal went to press.

Industrial action was averted last month when the Prospect trade union came to an agreement with management on terms and conditions and pensions.

Prospect is recommending that British Museum workers reject a pay offer through a ballot. Staff at the Museum of London have already rejected their pay offer and were due to ballot on strike action at the end of April.

The National Gallery has offered a two-year deal, but Prospect is recommending that employees reject the offer. Officials said all the pay offers were below the rate of inflation. Most pay grades are affected.

NMSI staff have been offered a below-inflation rise for 2007-08 and performance-related pay deal for 2008-09.

Emily Boase, the Prospect officer in negotiation with NMSI, said: "We recommended rejection because the offer didn't protect against cost of living. We oppose the introduction of 100 per cent performance pay."

She said an urgent meeting with NMSI management had been requested. In the ballot NMSI staff also indicated they would be prepared to take industrial action. Boase said: "We still want to reach a negotiated outcome but unless there is a substantial shift, we feel there will be strike action."

A Science Museum spokesman said: "We are still very hopeful for a resolution through negotiation. If there is a strike we expect all our museums to be open." Museum statement said: "If there is a strike, we expect all our museums to open."