Parliament has taken a lot of stick during the past eight years for its failure to challenge government. A smaller Labour majority and a clutch of new politicians should have changed that. The Commons has the chance to prove it is still an effective institution. But, as the House broke yesterday for a summer recess that will stretch until mid-October, there are few signs that such thoughts are bothering many MPs.

Dispiriting evidence lies in the saga of the setting up of Parliament's select committees. Ten weeks after the election, the committees - the main means of scrutinising government departments - were finally established last Wednesday. Only three have been able to start inquiries before the summer break; the rest will wait until the autumn. Given that the committees last met in March, this means a seven-month lay-off in Parliament's central function of holding ministers to account.

Much of the blame for the delay is aimed at government whips, who claim practical difficulties rather than conspiracy. And filling the committees is a complex task, like trying to complete 30 inter-related Sudoku puzzles simultaneously. But what's more concerning than the behaviour of the whips is the fact that virtually no MP has made a fuss about this gaping hole in parliamentary accountability.

Government will not willingly make life more difficult for itself - that's why Parliament exists. We know what to expect from whips, but we have a right to expect more from MPs.

The performance of the select committees, when they finally get underway, will be a weathervane for parliamentary effectiveness in this respect. Enabling MPs to work as cross-party teams away from the party political pantomime of the chamber, the committees offer a far more thorough form of scrutiny than anywhere else in Parliament.

Yet it is the behaviour of MPs that determines how well they work. And since 1979, when the departmental committee system was first created, their record has been patchy at best.

Two sets of developments offer new opportunities in this Parliament. Provided, that is, MPs are willing to use them.

First, committees are now better-resourced than ever. A new Scrutiny Unit was established in 2002, the committees have their own press office and around 50 new staff have been dedicated to select committee work. The chair of each committee has additional staff support, and departmental committee chairs were awarded an extra £12,500 to their salary in 2003.

Second, the numbers have changed. Labour's huge majority meant that previously each 11-member committee was divided thus: 7 Labour MPs, 3 Conservative and 1 Lib Dem (or an MP from a smaller party). Now that ratio changes to 6:3:2, giving Labour an overall majority of only one.

However, in a little-noticed sleight of hand the whips have increased the size of several key committees including Treasury, Home Affairs, Foreign Affairs and Defence. The whips suggest that the increase is merely a reflection of strong demand for places on these popular committees. But by going from 11 to 14 members, the Government retains a two-person majority in each of these important areas.

The members of these committees, and especially their chairs, must provide a genuine challenge to ministers in the next few years. Committees like Public Administration or Home Affairs have continued to shine a light into the darker recesses of government activity.

In contrast, the Foreign Affairs Committee is widely acknowledged to have underperformed over the past decade. In this crucial area, the committee has tended to chase an agenda set by government rather than probe more widely. But the committee system overall needs to aim higher. Here, a particular onus falls on the chairs of the select committees to earn their extra salary. Despite producing two excellent reports before the 2001 election, they have since been more concerned with their own individual committee territory than strengthening Parliament as an institution.

In the last Parliament, they started taking evidence from the Prime Minister twice a year. Undoubtedly an important development, it responded to the regular complaint from the backbenches that we're developing a presidential style of government.

But these sessions are a showpiece within the broader function of Parliament holding government to account. Most presidential systems are also characterised by complex systems of scrutiny and accountability. And it's only MPs who can make sure the committees provide those detailed checks and balances.

They must start by filling the gap in accountability that currently exists. One small suggestion is for all the committees, including Liaison, to meet during September. Although Parliament is not sitting, there is nothing to prevent committees from starting their enquiries, taking evidence or setting out their objectives over the next four years.

The steady decline of public trust in Parliament means that MPs cannot afford to miss the opportunities in front of them. It's not much perhaps, but how many committees decide to use September will tell us something about how serious Parliament is.

The writer was special adviser to two Leaders of the House of Commons, Robin Cook and Peter Hain, between 2001 and 2005