A remark in a Newmarket barber shop may prove instrumental in costing rail passengers more money to catch electric trains.

Transport Minister Steven Joyce has acknowledged being tipped off by his barber to the fact that it costs less to ride on Auckland trains than to catch buses over equivalent distances.

That has heightened his interest in a Ministry of Transport investigation into relative fare structures as Auckland prepares to receive a fleet of new electric trains, for which the Cabinet has approved a $500 million loan to KiwiRail.

Mr Joyce said his barber told him he loved travelling to work by train and, when asked why, explained they were cheaper than buses.

The minister said last month that he did not know the reason for the difference in fares, and was keen to find an answer.

Now, after the Government's final commitment to the $1 billion electrification project, he says he believes rail fares should rise to match those of buses to ensure ratepayers and taxpayers do not pay unfair subsidies.

Paul Harvey, manager of The Stylish Man in Broadway, has confessed to being the barber who let the cat out of the bag when he last trimmed the ministerial pate about a year ago.

He said he had no regrets about bringing politicians up to date.

"The more information they know from the everyday common man, the better for them, because sometimes they can become slightly removed from reality when it concerns how much it costs to live an everyday life," he said.

Single rail tickets from Manurewa to Newmarket cost $4.80, compared with $5.40 for buses,

Aligning rail fares to those of buses could mean an average 14 per cent rise for train passengers, although a spokeswoman for the minister said yesterday this would only would happen "over time as service levels improve".

Auckland Regional Council chairman Mike Lee said he supported any efforts to gain more "cost effectiveness and value for ratepayer and taxpayer dollars".

He hoped eventually that the costs of running the Auckland and Wellington rail networks would ultimately line up.

"I want our public transport system in Auckland to be sustainable over the long term - I don't want it top heavy with management and consultants that are not essential."

The minister's spokeswoman said Auckland rail passengers received a public subsidy of about $8 a trip, compared with $2.20 for their Wellington counterparts, although the capital is already served by electric trains with lower operating costs than diesel units.