Toyota has sold its millionth Prius hybrid in the US, six months after global sales of the world’s first mass-produced hybrid petrol-electric vehicle reached 2m and a month after the company announced that its total hybrid sales had passed the 3m mark.

The news came as Edmunds.com, the US-based auto data provider, announced that around 78,500 hybrid and electric vehicles were sold in the US in the first quarter, up from 57,200 last year.

The growth is attributed to rising petrol prices with fuel now averaging US$3.69 a gallon and predictions that it will reach as much as $5 a gallon by the end of the year.

According to Edmunds, sales of the Prius climbed 52% to 42,800 units while demand for Honda's hybrids surged 84% to 11,400 units.

“Since the Prius went on sale 11 years ago not a year has gone by when it hasn’t been the number one selling hybrid vehicle in the US,” said Bob Carter, Toyota Division group vice president and general manager. “Prius has become synonymous with the word hybrid and, as we see fuel prices starting to rise again, it has accounted for more than 60% of hybrid passenger car sales so far this year."