The number of people who believe they will buy a new car in the next three years has jumped to 71% – up from 55% last year, according to the latest AA Car Purchase Index.

The latest findings come as last month's new car registrations were the highest for a decade.

Of the 19,786 respondents in the AA Car Purchase Index who said they were going to buy a new car, 42% said they would choose a petrol engine, with 38% saying definitely diesel.

A further 13% don't know what fuel type they will opt for, but 7% will choose some kind of hybrid and 1% will go fully electric – a total of exactly 100 respondents. Last year only one person said they would buy a fully electric vehicle, suggesting a recent relative surge in awareness and popularity.

Men are much likelier to choose diesel, with 42% opting for it compared to only 29% of women. The Welsh are most likely to choose diesel with a 45% share, while Londoners are the most likely to go with petrol at 47% of the market.

David Bruce, director of AA Cars, says that although fuel prices were rising sharply up to three years ago, when diesel was the favourite fuel, the trend has since been downward although the gap between diesel and petrol forecourt costs had been widening.

'This has probably encouraged more people to opt for petrol but if the cost of diesel continues to tumble this might reverse the trend. At the pumps, diesel is at its lowest price since July 2012.

'But the fact remains that a litre of diesel, at 135.59p on average, still costs 6p more than petrol at 129.46p per litre.

'Frequent short stop-start trips don't suit modern diesels either – this can lead to [potentially expensive] problems with diesel particulate filter (DPF) blockages.

'So money is only likely to be saved by higher-mileage motorists where the economy of diesel cars overcomes the higher fuel cost,' he added.

The latest AA Car Purchase Index findings come as demand for the new 14-plate registration saw March reach 464,824 new car registrations, a rise of 17.7% over 12 months earlier and the highest monthly registrations figure for 10 years since March 2004 when registrations totalled 466,954.

March is typically biggest month and accounts for almost a fifth of full-year registrations. It saw registrations for the first quarter of the year up 13.7% to 688,122 units.