Drivers face an increase of up to 3p a litre on fuel prices, the AA has warned.
Experts say the recent price increases at the petrol pumps may be followed by more in the next couple of weeks.
Petrol prices have been creeping up again after more than three months of decreases and the AA has accused retailers of failing to fully pass on a 2p fall in diesel wholesale costs in November and December.
The Petrol Retailers' Association (PRA) said the recent rise in petrol costs was due to an unexplained leap in wholesale prices of 5p a litre since Christmas.
They suggest the rising prices at the pumps are due to "speculation" by traders in the wholesale market.
The AA warning comes as the Office of Fair Trading was today due to announce the findings of a review into whether reductions in the price of crude oil are being passed on to motorists.
Yesterday, motorists in Leicester said the expected increases would affect their livelihoods and family budgets.
Self-employed taxi driver Chris Banks said every time the price goes up at the pumps, his standard of living falls.
The 63-year-old from Clarendon Park said: "It has got beyond a joke now. The cost of fuel, which is essential to my business, just keeps on going up and up.
"I can't pass on the increase to my customers because I will lose business, so I have to take the hit. It's madness."
Carpenter Fitz Henry said the fluctuating price of petrol made every visit to the garage a lottery.
The 47-year-old from St Matthew's, in Leicester, said: "It just seems to change all the time.
"One week it is going down – but not very often – and the next week it is going up again."
Mum-of-six Londo Grace said the high price of petrol was eating into her family budget.
The 35-year-old from Humberstone said: "I need my car to get my children to school and to after-school clubs.
"There is no way I can do without the car, but it is just getting more and more expensive. The price needs to come down a long way and not go up again."
Lee Nicholls, who part owns the independent St Matthew's Garage in Humberstone Road, St Matthew's, said he had no choice but to increase his fuel prices yesterday by 2.5p per litre on diesel and 3p per litre on unleaded petrol.
He said: "There needs to be more clarity about what is going on when prices are set. It just seems so arbitrary."
Luke Bosdet, fuel price analyst at the AA, said: "It looks very much like there are further increases to come very soon on the forecourt. Whatever the reason, there has been an increase in the wholesale price of crude oil.
"This oil and refined fuel is sold in dollars and the pound is weak against the dollar at the moment, so that is helping drive prices up too."
