British car sales are expected to show a 30% drop for January when the figures are publised later this week.
The fall is greater than expected after a decline of between 20 and 23 % in recent months, reports The Times.
Meanwhile, Vauxhall is expected to announce large discounts across its range to attract buyers.
However the company, which is owned by General Motors, is thought to be raising its list price for cars sold in Britain because of the fall of the sterling.
Incentives will then be offered on the new list price.
Yesterday Ford announced its average price rises across its range of imported vehicles would be 4.7% because of the pounds weakness against the Euro.