LONDON (Reuters) - British new car sales fell by 6.9 percent in the first eleven months of the year due to stalling consumer confidence, stricter emissions rules disrupting supply and double-digit drops in demand for diesel, according to an industry body.

Demand declined 3.0 percent on the year in November alone, the Society of Motor Manufacturers and Traders (SMMT) said on Wednesday, and warned about the consequences of Britain crashing out of the European Union without a deal.

"It's now critical that a Brexit deal is secured to boost consumer confidence and provide a stimulus to the new car market as we enter the New Year," said SMMT Chief Executive Mike Hawes.

(Reporting by Costas Pitas, editing by David Milliken)