Figures from data firm Experian Catalist show the average price of a litre of petrol at UK forecourts reached a record 182.3p on Wednesday.
That was an increase of 1.6p compared with Tuesday, taking the average cost of filling a 55-litre family car to £100.27.
The average price of a litre of diesel on Wednesday was 188.1p.
Some forecourts are already selling petrol and diesel above £2 per litre.
He went on: “There’s almost certainly going to be upward inflationary pressure, which is bad news for everybody.
“While fuel prices have been setting new records on a daily basis, households up and down the country may never have expected to see the cost of filling an average-sized family car reach three figures.”
Mr Williams said many people will be hoping for further financial support from the Government as the 5p per litre cut in fuel duty “looks paltry” because wholesale petrol costs have increased by five times that amount since it was implemented in March.
“A further duty cut or a temporary reduction in VAT would go a long way towards helping drivers, especially those on lower incomes who have no choice other than to drive,” he added.
The AA called for a further 10p-per-litre cut in fuel duty and the introduction of a “fuel price stabiliser” which would see the rate lowered when prices rise, and increased when prices drop.
The firm’s president Edmund King said: “Enough is enough. The Government must act urgently to reduce the record fuel prices which are crippling the lives of those on lower incomes, rural areas and businesses.
“A fuel price stabiliser is a fair means for the Treasury to help regulate the pump price, but alongside this they need to bring in more fuel price transparency to stop the daily rip-offs at the pumps.
“The £100 tank is not sustainable with the general cost-of-living crisis, so the underlying issues need to be addressed urgently.”
Pump prices began to soar after Russia’s invasion of Ukraine in February led to oil supply fears.
The price of oil is continuing to rise due to increased demand for fuel across the world as China eases its coronavirus restrictions and the US and Europe enter the peak summer driving season.
Downing Street indicated on Wednesday that fuel retailers failing to pass on the 5p duty cut could be named and shamed.
The Prime Minister’s official spokesman said: “Transparency may have an important role to play.
“It is important the public understand what actions each of the fuel retailers are taking and so we are considering what further options we can take in this area.”