Now for the hard part. After the apologies, it is time to translate promises of reform into workable proposals. The danger is of rushing into tough-looking legislation with cross-party support that is inadequately scrutinised and flawed.

That is precisely the risk now with the new Parliamentary Standards Bill, which sets up a new independent authority to authorise MPs’ claims and regulate their financial affairs, backed by criminal sanctions, and new offences of false claims and registration. Ministers want this Bill to become law within four weeks, before the recess.

Gordon Brown is right that public anger over the expenses row requires a comprehensive plan. But talk of “root and branch” reform is no excuse for inadequate scrutiny.

The Bill has big constitutional implications. It not only transfers the administration of pay and expenses to the new Independent Parliamentary Standards Authority. The Bill also makes the Ipsa responsible both for setting the rules on financial interests and expenses, and, via a new Commissioner for Parliamentary Investigations, for examining potential abuses.

The final power to decide on non-criminal penalties will still lie with MPs. But self-regulation is being heavily qualified in practice. There are also questions about the legal status of the new and more wideranging code of conduct.

The biggest question is how far the creation of the new authority by statute will open the way for a flood of judicial review cases. This is in contrast to the present position whereby the Parliamentary Commissioner cannot be challenged since the post was established by a Commons resolution and is therefore exempt under the 1689 Bill of Rights. Officials argue that such court challenges should be limited because there is an appeals process and the House ultimately decides on sanctions. Moreover, the broader provisions of the code are intended to be declaratory and non-justiciable.

Even if the present mood of public atonement will result in speedy passage of the Bill in the Commons, the Lords may raise more questions, not least because peers fear that these arrangements may apply to them before long.

This is not an argument against the Bill, but rather for an extension of the timetable to permit adequate scrutiny. Just remember the Dangerous Dogs and Child Support Agency Acts, passed rapidly with widespread support. Legislating in haste for however worthy an aim is usually counter-productive and goes against talk of strengthening the Commons.

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