British workers at Unilever walked out on strike across five sites on Wednesday in a pensions dispute while the consumer goods group reassured customers that it had stockpiled supplies to ensure no shortages.

The world's third-largest consumer goods group, maker of Persil detergent, PG Tips and Colman's mustard, said its staff were taking strike action at three production plants and two support sites, while workers at a third office site were taking limited working to rule action.

Workers are angry that Unilever is axing its final-salary pension scheme which will hit pensions for 5,000 of the group's 7,000 British employees, and the action follows the first strike in Britain in the group's 82-history last month.

Around a third of Unilever's British workforce are union members and were involved in strike action from early Wednesday at the group's Purfleet Flora and Hellmann's plant, its Warrington detergents factory and Norwich Colman's facility.

Unilever is looking to move workers on a promised final salary pensions scheme to a less generous average career scheme by July 2012, and argues this scheme is very competitive with rival companies and 90 percent of affected staff will retain 80 percent or more of their previous pensions.

Concern over pension changes is growing in Britain and an industry survey in December showed a quarter of such final salary schemes are now shut to new staff and former existing members. Unilever says rising life expectancy and market volatility mean pensions based on final salaries are outdated.

Three of Britain's biggest unions Unite, GMB and Usdaw have called for 11 days of rolling strikes across Unilever's 12 sites in England and Wales which will finish at its Pot Noodle factory at Crumlin in south Wales at midnight Saturday evening, Jan 28.

We are seeing a fantastic turnout and getting messages of support from the public and other unions, said Unite's Jennie Formby speaking on the picket line outside Unilever's large research and development facility at Port Sunlight in northwest England where there are around 450 union members.

(Reporting by David Jones; Editing by Mike Nesbit)