Toyota GB managing director Miguel Fonseca is expecting the total market for car sales could drop to 1.7 million in 2009.
Fonseca said: "Our numbers are down quite a bit in November.
"The indications are that other manufacturers are suffering as well."
But he believes Toyota may not be as badly affected as some in 2009 and is aiming to keep the company's market share at around 8% thanks to a raft of new models and environmentally friendly cars.
In January alone there will be three new models starting with the new, Burnaston-built Avensis which started rolling off the production line at the end of last week.
Fonseca admits that this may not be the best time to launch a D-segment car, but his sales targets, he adds, are realistic.
Toyota plans to sell 14,000 Avensis saloons and estates in the UK in 2009, down from a peak of 18,000 in the early 2000s.
Fonseca said: "We will also be selling 10,000 Prius Hybrids so our market share in the D-segment will actually be increasing.
"As for small cars, we will be launching the iQ in January as well as the 2009 Yaris. Later in the year there is the new Verso and updated RAV-4 and Prius.
"This year has been fairly quiet for us and I think we will benefit from all the new models arriving in a falling market in 2009."
The luxury Lexus brand should also benefit with the arrival in June of the updated RX hybrid - Fonseca confirmed that only hybrid versions of the SUV will be imported from next year, as well as the IS convertible in the same month.
He said: "We have not finalised our sales numbers for next year but we will be concentrating on higher value business, more retail sales, fewer fleet sales. We will have a lot of new products with low CO2. We will also be looking at cost management throughout the business.
"The market will be lower but people will still be buying cars because mobility is not a luxury."