A union official has told BMW workers complaining about longer hours that they should knuckle down for the good of the company and their futures.

About 100 new jobs are set to be created at the Mini factory at Cowley in Oxford if workers accept a new shift system.

Spiralling demand for the car has meant managers are trying to find ways of increasing production.

They have already added an hour to the weekend shift at the factory, which was today unveiling the 500,000th car to roll off the production line.

The extra hour has proved unpopular with some workers, who are now being urged to accept another increase in hours on the early shift, which would allow the recruitment drive to be launched. But union leaders are backing the move, which will be put to the affected workers in the body in white and paintshop areas next Wednesday.

Transport & General Workers' Union convenor Bernard Moss said: "Demand is going up and up and we're nearly at maximum production -- we can't turn volume down.

"We recognise people are having to work hard and doing long hours, but we're in a unique situation.

"Volumes are going up and up, whereas other manufacturers are reducing shifts and getting rid of workers.

"Success comes at a price. If you turn the work down, you're turning down the future."

The proposed shift change will mean workers will be asked to do more early shifts in return for a reduction in the number of unpopular Friday evening shifts.

Mr Moss said it would be possible for staff to earn up to £29,000 a year under the new system. BMW plant spokesman Werner Rothfuss said: "The purpose of the whole thing is to find a way of increasing production. If we extend the number of hours individuals work, then we have to extend the number of individuals and so there are more job opportunities."

Latest figures show the total number of Minis delivered worldwide rose by four per cent to 110,843 in the year to July 2004.

High demand for the car has led to waiting lists of almost a year for the recently launched Convertible model. BMW managers are applying for permission to extend into the Green Belt by developing the adjacent sports ground at Roman Way, Cowley, with a new bodyshop, and plan to increase use of the railway sidings at the factory for deliveries of parts and engines.

Meanwhile, the keys to the 500,000th car were being handed over to American customer Dan Cowdry by plant managing director Anton Heiss at a special ceremony today, attended by Oxford East MP Andrew Smith and Lord Mayor Bryan Keen.

Mr Cowdry, 35, and girlfriend Kossondra were flown in as special guests by BMW and will spend four days in Oxford.