The Prime Minister plans to “expose” petrol stations that fail to pass on lower fuel prices from the Government’s fuel duty cut, it has been reported.

The Government introduced a 5p per litre duty cut on March 23, but this week figures showed average petrol prices exceeded £1.70 per litre for the first time.

Retailers have been accused of raising profit margins since the policy was introduced.

The RAC accused petrol retailers of taking advantage of customers by not passing on lower wholesale prices.

The motoring organisation described December as a “rotten month” for drivers who it claimed could be being overcharged by £5 million a day for petrol.

Petrol prices dropped by 2p per litre over the month although the organisation said drivers should have seen a roughly 12p fall.

RAC fuel watch figures showed that the price of unleaded dropped from 147.47p a litre to 145.48p.

However, it added that drivers should have witnessed prices “nearer to 135p”.

Simon Williams, fuel spokesman for the RAC, said: “The 10p extra retailers have added to their long-term margin of 6p a litre has led to petrol car drivers paying £5 million more a day than they previously would have.”

The Sunday Telegraph reported that Johnson has ordered Department for Transport officials to draw up plans to target petrol stations that choose not to pass on the 5p fuel duty cut to customers.

According to the paper, Transport Secretary Grant Shapps has suggested a “pump watch” name-and-shame scheme. Ministers reportedly opted against the idea of a windfall tax for petrol retailers.

A Downing Street source said: “Officials are considering mechanisms available to expose those companies that aren’t passing on tax benefits to consumers.”