In April Britain's biggest union said it would hold a total of eight strikes, with walkouts at both the Mini and Rolls-Royce factories as well as an engine plant, but suspended further action last month to allow staff to vote on a revised deal.

Unite said on Monday that members had rejected an offer which proposed closing the scheme but offering a cash payment of 22,000 pounds over three years or 25,000 pounds paid into a new defined contribution pension scheme.

"We expect to meet BMW in the coming days," said Unite National Officer for BMW Fred Hanna on Tuesday.

"Shop stewards from all of BMW’s UK plants are clear that further strike action is almost certain unless the company puts forward a new offer that better addresses members’ concerns," he said.

BMW said on Monday its revised was fair and would improve competitiveness and would meet with workers' representatives in due course.

(Reporting by Costas Pitas; Editing by Greg Mahlich)