A Sussex MP has learned that more than £17,000 was spent trying to stop him finding out what other Members of Parliament claimed for travel expenses.
MPs can claim for daily journeys to and from work
Norman Baker, the Liberal Democrat MP for Lewes, asked for the figure under the Freedom of Information Act (FOI).
He discovered the money was spent on two appeals to try to prevent him from getting the information.
The details of claims made by MPs were published last month after his two-year battle with Commons authorities.
They had argued that publishing a detailed breakdown of claims could breach data protection rules, but were overruled by the Information Tribunal.
Speaking to the BBC on Monday, Mr Baker said: "We're all accountable, it's all public money and the public at large have a right to know how their money is being spent.
"Secondly, I was concerned at what was likely to be some of the excessive claims and I wanted the travelling expenses broken down by mode of transport also."
The MP said the authorities - senior members of the House of Commons who sit on the Commons Commission - had "fought tooth and nail to resist almost every application for information about MPs".
He added: "The attitude they have is wholly out of line with the sentiments of the FOI and therefore it does worry me because there's a cultural problem here among those MPs."
Defending his two-year campaign, Mr Baker said it had been a "proper request within the bounds of the Act".
"It was not intruding on the privacy of MPs and should have been answered.
"Instead they used every single tool available to fight it and the result is a £17,000 bill for the public," he said.