The authorities will look again at whether forcing motorway service areas (MSAs) to display their fuel prices would result in lower prices for motorists.
The decision was revealed in a letter to the transport secretary Chris Grayling from Andrea Coscelli, chief executive of the Competition and Markets Authority (CMA).
Coscelli was responding to a letter from Grayling calling for an investigation into “exploitative” motorway fuel prices.
Grayling said: “I would welcome a view from the CMA on whether the three private companies that currently operate the majority of MSAs are exercising market power to the detriment of motorists.”
Coscelli pointed out the CMA’s predecessor, the OFT, had carried out an inquiry into fuel pricing in 2013, and found there were legitimate reasons for the higher prices at MSAs.
However, it also called for more information for motorists to promote competition between MSAs, and said there was evidence roadside signs had helped to reduce prices in other countries.
But a trial run by Highways England at five MSAs in the South West that began in 2016 concluded there was no overall effect on prices, and Coscelli said the CMA would work with Highways England and the Department for Transport to see whether wider use of signage might work.
He added: “I believe the quickest and most effective way of a having a positive impact for motorists is to work together on this matter now. We will be in a position to identify effective measures to help motorists much sooner this way than if we undertook a formal investigation.”