Manganese Bronze, the firm which makes the distinctive London taxi, has said it made no profit in 2011 and could fall short of expectations for the current year.
The group blamed the weak UK economy, uncertainty over the global economic outlook and a delay in fulfilling an order for 1,000 taxis from Azerbaijan.
The firm sold 1,502 taxis in the UK last year, compared with 1,653 in 2010, a fall of 9.1%, it said.
But overseas sales were much stronger.
The company sold 705 vehicles compared with 226 in 2010.
In March last year, the firm secured a $27m (£18m) order from Azerbaijan - its single largest order to date.
However, a delay in shipping the second half of this order, which was meant to be dispatched in October, means the company will not record a profit in 2011.
"The overall impact of lower UK sales and a delayed fulfilment of the Azerbaijan order will prevent the group from achieving a profitable result for the year ended 31 December 2011," the company said in a statement.
It had previously said it expected to return to profit last year.
"Whilst a proportion of this shortfall should be recovered when the delayed Azerbaijan sales are recorded in 2012, any continued softening of global economic conditions would mean that the group is likely to fall short of meeting expectations for the current year," the statement continued.
Chinese car group Geely owns 20% of Manganese, which switched production from Coventry to China as part of its restructuring.