Sales of the Cowley-built Mini plummeted sharply last month as the factory enforced an extended shutdown over the Christmas period.

December’s worldwide sales were down 27.8 per cent to 15,010, compared to 20,800 the previous year.

However, annual sales rose 4.3 per cent to 232,425, thanks to a good performance earlier in 2008.

The four-week Christmas shutdown — two weeks longer than normal — was planned in response to “challenging economic times”, said factory owners BMW.

The plant is due to close later today and not re-open until Monday.

BMW spokesperson Rebecca Baxter said: “We are facing challenging economic times and we are obviously monitoring the situation. But the fact remains that Mini is a strong brand.”

She said the annual figures were encouraging and added: “Despite the difficult economic conditions we have got to the end of the year and Mini sales are up across our global markets.

“We sell to nearly 80 countries around the world and one of the reasons for the increase is the strong US market.”

Mini sales in the US were up 0.1 per cent in December, she said.

She added: “We started the year well, but there was a slowdown towards the end of the year.”

The Cowley plant's 4,500 workers make Minis to order, so any downturn in sales has an immediate effect on production levels.

In December, the Oxford Mail revealed that UK sales of the Mini had fallen by 13 per cent for the year to date, while the total UK car market had slumped by 11 per cent in the same period.