Unions seeking to give Carrefour CEO Lars Olofsson an "uncomfortable" Christmas.

Carrefour's French stores could be hit by strikes in the run-up to Christmas and possibly for longer, amid continued opposition by unions to plans to introduce new work patterns.

One of Carrefour's minority unions, the CGT, has called on its members to stage a one-day stoppage on 18 December against proposed changes to night shifts.

Industrial action is also planned for next week when Force Ouvrière, which accounts for almost 50% of Carrefour's unionised staff, begins what a spokesman said was "a six-month campaign to protest its total opposition to management moves to re-organise work patterns to the detriment of staff".

The six months to May correspond to the duration of the test period for the proposed changes set by Carrefour, the spokesman said.

"Each week, our members working in two the three strategic hypers in a specific region of France will strike, beginning with Brittany next week, followed by stores in the Paris region. We want to make (Carrefour chief) Mr Olofsson's Christmas an uncomfortable one," he said.

Carrefour declined to comment on the likely impact of industrial action.