Conducted between December 2013 and March 2014, the independent research organisation sent 19 secret shoppers to 85 dealerships in four states, following reports that some dealers were pushing customers towards petrol models instead of plug-ins.

Dealers were asked a set number of questions about tax breaks and incentives, charging, battery life, warranties and whether to buy or lease, and stock levels of plug-in vehicles were recorded as part of the study.

Of the 85 dealers, the secret shoppers noted that 13 discouraged buying an electric vehicle and 35 encouraged them to buy a petrol car instead. Only 15 of the dealers visited had more than 10 cars available in their inventory to view, while 21 explained this by saying the cars were popular and had sold out. Behind this, many cited a lack of consumer interest as a reason for not carrying large stock levels.

Consumer Reports also said the advice given varied depending on the manufacturer’s preference for electric or hydrogen fuel cell models. Chevrolet, Ford and Nissan dealerships were better informed than Honda or Toyota, correlating with the model range available.

However, it added that there were variations across the country. One Californian Toyota dealer said the Prius Plug-in needed a new battery every two years, while a Ford dealer in New York said the Focus EV doesn’t exist and couldn’t be leased, neither of which is accurate.

The report added that this was sometimes in the customer’s interest, including a Nissan dealer who diverted one secret shopper away from a LEAF because their usage would have stretched the limits of its electric range.

Eric Evarts of Consumer Reports said: ‘If you're shopping for a plug-in car—or any car, for that matter—do your homework and don't rely on the dealership for education about this intriguing technology. Instead, use the visit for hands-on experience necessary to make the best buying decision.’