Is Norman Baker the most hated man in Westminster?

Norman Baker might be well advised to keep a low profile when MPs return to Westminster from their half-term break next week.

The Liberal Democrat MP is celebrating a memorable victory after a two-year battle to obtain a detailed breakdown of how much every politician spent on travel by car, taxi, air, train and even bicycle.

But not every one of his 645 parliamentary colleagues will be quite so delighted at his success in shining a spotlight on to their expenses claims.

Janet Anderson, the Labour MP for Rossendale and Darwen, will not have been relishing exposure as the most enthusiastic motorist in the Commons, submitting a £16,612 mileage claim last year, the equivalent of covering 60,448 miles.

She was not returning calls yesterday but another Lancashire MP remarked acidly: "Janet has always loved her car."

Tory MP Mike Penning claimed £7,978 for mileage, although his Hemel Hempstead constituency is less than 30 miles from London. And Diane Abbott, the Labour left-winger who represents Hackney North & Stoke Newington, some five miles from Westminster, received £2,235 in car hire and taxi fees.

There might also be a certain froideur in the air when Mr Baker next bumps into Chris Huhne, his successor as the Liberal Democrat environment spokesman. Mr Huhne spent £3,284 on car mileage - but only £176 on train tickets, even though his Hampshire constituency is easily reached by rail.

But Mr Baker, regarded as a leading member of the Commons "awkward squad", is unrepentant over ruffling fellow politicians' feathers.

He said: "Perhaps there are colleagues out there who aren't very happy but that's not my priority. I'm going places where other MPs find it uncomfortable to go, but someone has got to do it."

Although he started working life as a director of a record store chain - and has an encyclopaedic knowledge of 1960s pop - he soon became immersed in Liberal Democrat politics.

He first came to the party's attention as a tenacious environmental researcher in the Commons.

After a spell away, he returned as the MP for Lewes and began building a reputation for burrowing away in Whitehall's darker corners. In his first three months as a backbencher he asked more Commons questions than his Tory predecessor had in 23 years.

He burst to national prominence six years ago after playing a leading role in triggering Peter Mandelson's second Cabinet resignation with his questions over the passport application of billionaire Dome sponsor Srichand Hinduja.

He stood down from his environment portfolio in 2005 to pursue wider political interests, such as opposing replacement of the Trident nuclear missile system and investigating the "unanswered questions" over the death of Iraq weapons inspector David Kelly.

Mr Baker is passionate about using the Freedom of Information Act to force greater transparency in public life and, this week, he scored by obliging the Commons authorities to disclose detailed travel expenses.

That is causing reverberations within Westminster. Richard Bacon, the Tory MP said to have claimed £5,865 for taxis, said he had referred the accounting methods used to compile the statistics to the National Audit Office. He described the figure as ludicrous, adding: "I applaud Norman Baker's efforts to secure greater disclosure. I would also like any published figures to be accurate."

Labour's Eric Joyce, who had the highest overall travel expenses claim, said he did not believe the figures were "feasible".

Meanwhile, the TaxPayers' Alliance said it would write to Sir Philip Mawer, the Parliamentary Standards Commissioner, asking him to investigate "a number of MPs who appear to have been abusing the system".

And Friends of the Earth said the publication of the figures gave politicians the chance to prove their green credentials. Tony Juniper, its director, said: "It's important that our MPs show leadership by cutting down on their own carbon footprint by using public transport whenever possible.

"They have a real opportunity to make it easier for the rest of us to do the same by using their positions to influence a climate change law that favours less polluting forms of travel."

The fearless investigator

Jan 2001 Receives Commons written answer stating that Peter Mandelson "made inquiries" about how a passport application by Srichand Hinduja, a sponsor of the Millennium Dome, might be viewed. Led to Mr Mandelson's second Cabinet resignation.

Oct 2001 Uses rights under the Data Protection Act to win High Court test case forcing MI5 to open secret files for the first time in its 92-year history.

Dec 2002 Compiles figures that disclose that the Government's car fleet has grown to 207 - the largest number on record.

May 2003 Obtains letter warning Cabinet Ministers they need to spend £10m to prevent radioactive leaks from Sellafield nuclear power station.

Jan 2004 Finds the Foreign Office spent £746,000 on art in 1997-2001.

Jan 2005 Begins campaign to force disclosure of MPs' expenses under Freedom of Information Act.

Jan 2006 Begins investigating David Kelly's death. He believes the Iraq weapons expert could have been the victim of a murder that was covered up.