London black cab maker Manganese Bronze in £4m IT error
A manufacturer of London black cabs has revealed a £4m hole in its accounts and warned of mounting losses.
Coventry-based Manganese Bronze saw its shares fall 34% after saying it expected "substantially higher" losses for the first half of the year.
The company blamed the accounting mistake on its new IT system, which meant losses, dating back several years, had been understated by £3.9m.
The company has delayed announcing its half-year results until next month.
Manganese said a combination of "system and procedural errors" meant a number of transactions and balances were not transferred to the new IT system when it was introduced in August 2010.
The company, 20% owned by Chinese car maker Geely, has struggled due to weak demand over the past few years.
In 2011 it reported a 9.1% drop in UK sales, although overseas revenues were stronger.
Manganese said it continued to trade at a loss as conditions remained "challenging".
It predicted higher sales in the second half of the year, but said it was unsure if it would be on track for its full-year forecasts.
The company is due to introduce its new Euro TX4 taxi, designed to meet new environmental targets set by London Mayor Boris Johnson.