US President Donald Trump said on Wednesday that he has instructed the Department of Justice to look into oil companies for ​not lowering gasoline pump prices in line with falling crude costs, ‌and accused the companies of “gouging” customers.

Trump did not name any companies in his social media post, which came after midnight. The White House and the Justice Department (DOJ) did not respond ​to a request for further comment outside regular business hours.

Diplomacy between the ​US and Iran has translated into relief at the pump for ⁠Americans, data showed earlier this week, with gasoline prices falling for a sixth ​straight week.

However, Trump said the fall in gasoline prices was neither enough nor ​proportionate to declines in crude oil costs.

“Gasoline prices better start going down a lot faster than what I’m seeing!”

Trump’s latest post comes as consumers raise concern over high gasoline prices, just ​as the president and fellow Republicans are battling to hold narrow majorities in ​Congress in November’s midterm elections.

The average price of gasoline in the US was $3.906 per gallon early Wednesday, ‌GasBuddy ⁠data showed, down more than 14% from the peak in May.

By comparison, over the same period, crude oil prices have fallen 23%, with the US and Iran reaching an interim peace deal and reopening the Strait of Hormuz, through which ​one-fifth of global oil ​supply moved before ⁠the war began.

From their peak in March, US crude prices have sunk about 40%.

“The big Oil Companies are not ​dropping their price at the pump commensurate with the sharply ​lower prices ⁠they are paying for Oil. Those prices are dropping like a rock! In other words, customers are being “gouged”,” Trump said in a post on Truth Social.

“I have instructed ⁠the ​DOJ to immediately start looking into this.”

Pump prices ​remain significantly higher than the $2.764 per gallon recorded in January, more than a month before the Iran ​conflict began.