Union sources are today claiming that some 40,000 General Motors workers are taking "unofficial action" in support of colleagues at the Vauxhall plant in Luton, England.

Some 2000 workers will lose their jobs when Vectra production ends next year, though about 500 could be offered a transfer to the GM-Renault joint venture van plant next door.

An unofficial strike would be illegal in Britain ahead of a union-organised ballot expected to be called next week so GM Europe Works Council officials encouraged staff to report in sick today.

The sources say that no-one turned up for the 6am shift at either the Luton Vectra plant or the adjacent IBC van plant. Workers did show up for the 7am shift at the Ellesmere Port Astra and engine plant but downed tools and walked out "arm in arm" at 11.30am. GM is likely to lose production of 800 cars in Britain as a result.

Plants across Europe are also affected, the sources say, with about 40,000 of GM's 60,000 workers taking the day off. Locations where GM workers are supporting their Vauxhall colleagues include the Corsa factory in Zaragoza, Spain, a Portugese assembly plant, four German car and engine factories and the Astra assembly facility in Antwerp, Belgium.

Vauxhall spokesman David Crundwell said "very few" of the first shift at Luton had turned up. He would not comment on the likelihood of the second shift showing up but said that Vauxhall did not expect to build any cars there today.

About one-third of the IBC workforce had arrived but the plant was not scheduled to make any vehicles today as it is preparing to produce a new van model developed jointly with Renault as well as re-instating Frontera production facilities after the proposed move to Ellesmere Port was halted in the December restructuring of GM Europe operations.

Crundwell said that there had been some production at Ellesmere Port this morning until around 11.30am when staff walked off the assembly lines. He would not comment on the chances of production resuming with the arrival of the second shift later today.

Earlier, Associated Press reported that nearly 4,000 workers rallied outside the main Opel plant at Ruesselsheim near Frankfurt, according to police estimates.

Guenter Lorenz, a spokeman for Germany's IG-Metall auto union, told AP it was important for all European workers to show solidarity with the employees targeted for layoffs, and said workers at all European GM facilities were encouraged to lay down their tools.

"Any plant in Europe could itself be the next one affected," Lorenz said.

Apart from the 2000 Vauxhall posts, GM is trimming 3,000 jobs in continental Europe, including 1,700 at Opel. As well as axing assembly line workers, GM will cut salaried management and administrative staff by 10 percent.