The price of unleaded petrol jumped to as much as 124.9¢ a litre across Melbourne on Friday, an increase the state's peak motoring body says is unjustified.

Petrol has been at six-year record lows for the past three months in Melbourne and the city's average price was 102¢ per litre as recently as Sunday.

But the price had risen to 124.9¢ a litre at number of service stations on Friday, including at a 7-Eleven service station in Chirnside Park, a Caltex station in Diamond Creek and a BP in Dandenong South.

Brian Negus, the RACV's general manager of public policy, said around 7.6 per cent of monitored service stations in Melbourne had increased their price to 125¢.

Despite the price hike at some bowsers, Mr Negus said almost three-quarters of the market was still selling petrol below 102¢ a litre.