The Lowdown: Mess about and you'll be in detention

He went from the chalkface to the Commons. Heather Tomlinson meets John McFall, chairman of the Treasury Select Committee

previous career as a chemistry and maths teacher has proved useful for John McFall in his role as chairman of the House of Commons Treasury Select Committee.

When he was deputy head of a Scottish comprehensive, McFall made unruly youngsters toe the line. His worst punishment, he says, was to order a wayward pupil to follow him around all day. "It's only beaten by an appearance before the committee," he laughs. Gordon Brown, who is often called to account by McFall's star chamber, no doubt agrees.

To be grilled by the committee is certainly an uncomfortable experience. McFall, the Labour MP for Dumbarton, is not a man to break in his interviewees gently. He has chaired the committee since July 2001, and has brought his classroom skills to bear in his dealings with business leaders, regulators and government ministers.

In November the committee accused Sir Howard Davies, the head of the Financial Services Authority, of being "asleep on the job" during the scandal that erupted over split capital trusts. Certain companies in the market had built up a house of cards of heavily indebted investment trusts, each invested in one another, which has now collapsed.

Last week McFall called for the investment trust industry to compensate those who are suffering financially. "Those individuals who are elderly, and in need of financial assistance comparatively quickly, shouldn't be allowed to wait until the matter is dragged through the courts," he argues. "The investment trust industry has an obligation to establish a compensation scheme, so it can best assist those in most need early on. It would be a gesture of goodwill on the industry's part."

Another man to get the McFall treatment is Sir Edward George, the Governor of the Bank of England, who gave evidence to the committee last month. In an interview worthy of Jeremy Paxman, McFall asked Sir Edward to comment on the disproportionate rise in directors' pay, no less than nine times. "The Governor ducked out of the answer that day, but it's something I have not forgotten," warns McFall. "If you look at levels of executive pay over the past few years, at a time when productivity and company profits haven't been increasing, they've leapt ahead of the rest of the workforce. You've got to ask why. To date I have been given no satisfactory answer." He has called for the Government to come up with a response.

At a previous round-table discussion on corporate governance, McFall's outrage boiled over. Mismanagement had led to the bankruptcy of the photo film and camera manufacturer Polaroid, causing job losses within his own Scottish constituency. He claims the US company's drive to boost profits was given precedence over vital research and development. "So you heard me shouting that night," he says wryly.

But face to face, McFall is affable and softly spoken, with a strong Scottish accent and an impressive ability to hold an unbroken conversation while whizzing through a mountain of paperwork.

He's a busy man. The committee is about to investigate the lack of transparency in credit card charges, and has recently criticised the Government's treatment of Network Rail, the non-profit company that has replaced the failed Railtrack. It has also questioned whether Gordon Brown's forecasts for economic growth are too optimistic.

The Conservative Party often jumps on such comments as criticism from a "Labour-dominated" committee. McFall may be a former minister, but he sees his present role as more important. "We have a situation, with a parliament with a large majority, where it is incumbent for select committees to scrutinise the executive in an objective way," he says.

McFall is one of many Labour MPs who support a war with Iraq only if it is sanctioned by a UN resolution. Otherwise, his personal politics mostly tie in with the New Labour philosophy.

He is in favour of a partnership between the state and the private sector to deliver public services, although he argues that the Government must do more to convince the Labour Party of the benefits. He agrees that additional funding for public services can come only from sound management of the economy and not through hiking up taxes.

He is also pro-euro, and his committee is now preparing a report that will simplify for the general public the complicated issues surrounding entry into the single currency. "I don't think there's any option," he says. "We must be a member of the euro at some stage.

"Gordon Brown's approach, in making the economic case, I think is the right one," he continues. "If you look at the history of sterling in the 20th century, we made massive mistakes from 1925 onwards, from the restoration of the gold standard, through to the devaluations, to joining EMU. They were all done with scant economic analysis. [This time] we need to have a more thorough economic investigation because this decision will be irreversible and will last for centuries."

However, McFall has written to the Chancellor to ask him for more transparency on the five "economic tests" that are to be the basis for the Government's decision on when to join the euro.

On the failures of the financial sector, McFall has been more outspoken. It's an issue that touches him personally: he is himself a victim of the Equitable Life debacle. "I've a small savings policy, and I'm still staying the course. It's a with-profits, or a with-less-and-less-profits policy," he jokes.

He may now be very much at the centre of political life in London, but McFall was born and bred in his constituency, and knows many of his electorate by name. His friends and even his wife have questioned why he gave up his "sensible and productive" teaching career for the "hot air" of Westminster. But he has no regrets. The City grandees and government officials he grills probably wish he was still focusing his attention on disruptive elements in his classroom.