The Government’s announced next year’s rise in English rail fares will be below 9%.
Any increase will be below the rise in the Retail Prices Index (RPI) measure of inflation for the 12 months to July.
On Wednesday, the Office for National Statistics said that figure was 9%.
The Department for Transport said any change to fares will be implemented in March next year.
It has not revealed how it will be calculated.
Treasury minister John Glen told Sky News: “We have said that we will keep it below inflation.
“Obviously I will be working closely with Mark Harper, the Secretary of State, on what mechanism to use.
“But there are tough decisions now around how to use his budget in a way that suits commuters and suits the economy as a whole, delicate difficult decisions.
“We have not come to the end of that discussion yet.”
The Government used the UK’s average earnings growth of 5.9% during the quarter to July 2022 to determine this year’s increase in fares.
The figure for July this year will be published on September 12.
Average earnings growth in the three months to June was 7.8%.
About 45% of fares on Britain’s railways are regulated by the Westminster, Scottish and Welsh Governments.
They include season tickets on most commuter journeys, some off-peak return tickets on long-distance journeys and flexible tickets for travel around major cities.
Train operators set rises in unregulated fares, although these are likely to be very close to changes in regulated ticket prices as their decisions are heavily influenced by governments due to contracts introduced because of the coronavirus pandemic.
The Scottish and Welsh Governments have not announced their rail fares plans for 2024.
Fares in Northern Ireland are set by operator Translink.