ScotRail said the claim “book direct for our best price” referred to the fact that consumers who booked directly with ScotRail always paid the lowest price it offered.
A spokesperson said the rail industry operated under regulated fares with a centrally-controlled fares database from which all accredited retailers sourced their ticket prices.
They said they applied no additional booking fees to those standard fares, unlike some third-party retailers and competitors, which meant they could guarantee their best price when a consumer booked with them directly.
The ASA ruling said: “As stated, we considered the overall impression of the ad was that consumers would be able to find the cheapest ticket for a particular journey on the ScotRail website.
“As such, we considered that the claims ‘get cheapest tickets’, ‘book direct for our best price’, and ‘unbeatable on price’ discouraged consumers from searching elsewhere for cheaper tickets.
“However, they provided no evidence that, through purchasing tickets separately on the ScotRail website, they would always beat competitors’ prices.”
The ASA said that the ad must not appear again and told ScotRail to ensure they do not mislead consumers by claiming they could offer the lowest price available if that was not the case.