The dark clouds over General Motors, Ford Motor and Chrysler appeared to be lifting a month ago, but a new squall has engulfed the Detroit carmakers.

Their stock market performance reflects the change. GM shares touched a three-year high of $43.20 on October 12 after winning concessions from the United Auto Workers union. Carmakers had also made progress in other areas, such as revamping car rental sales, improving their discounting discipline and financial restructuring. But by early last week GM shares had fallen 40 per cent while Ford shares were down a fifth. Both regained some losses on Friday.