Will the Hutton inquiry lead to more open government - or will ministers find this shot of freedom of information so bitter they will do everything possible to avoid it in future?

The level of disclosure at an inquiry like this goes beyond that which a freedom of information act would normally provide. FOI laws balance the right of access against exemptions, one of which invariably gives government some privacy for its internal thinking. The material we are now seeing is not filtered in this way, and that is what makes the hearings so compelling. Officials explain how scrupulously they have behaved, only to be undermined by the disclosure of a memo or email revealing that what they did was precisely the opposite.

We have of course been here before. The Scott inquiry revealed that the Conservative government had relaxed restrictions on arms sales to Iraq but concealed the new policy. With breathtaking frankness, the former foreign secretary, Lord Howe, explained that the government should not be criticised for "incompatibility between policy and presentation of policy". Scott reported that "in circumstances where disclosure might be politically or administratively inconvenient, the balance struck by the government comes down, time and time again, against full disclosure".

Similar failings were revealed by the BSE inquiry. The Ministry of Agriculture had adopted a policy of "positive censorship" about the new disease, preventing its scientists even discussing their findings with outside experts. The inquiry reported that "had there been a policy of openness rather than secrecy, this might have led to a better appreciation of the growing scale of the problem and hence to remedial measures being taken sooner."

You can draw straight lines from those inquiries to this one. The inability to trust the public with the facts is still there. We were told we went to war against Iraq because of the intelligence. We now see that the decision was taken on other grounds - and the intelligence squeezed into a shape to justify it.

The Scott inquiry led Labour to strengthen its historic commitment to freedom of information. In 1996 Tony Blair announced "if the case was not unanswerable before, Scott has made the case for a freedom of information act absolutely unanswerable now, not just because of how it might have applied in the specific case but also because of the sea change it would bring in attitudes towards the release of information".

So where's the sea change? The Freedom of Information Act was passed nearly three years ago, but the right of access has been delayed until 2005. While many public authorities are making serious efforts to prepare for the new law, Downing Street itself gives the impression of being at best indifferent and possibly hostile to the legislation.

In July the parliamentary ombudsman reported that the government had blocked two open government investigations, both touching on ministers' integrity. The prime minister's office refused to comply fully with the ombudsman's recommendation that it release a list of gifts received by ministers. The ombudsman revealed that the lord chancellor, who favoured disclosure, had been overruled when Blair's chief of staff, Jonathan Powell, decided that press coverage of a "huge list of gifts" would be embarrassing. In the other case, the Cabinet Office issued a formal ministerial veto to certify that any disclosure about ministerial declarations of conflict of interest would be "contrary to the public interest".

So why should anything change? Perhaps because the mistrust of government has now reached levels that even Downing Street must find alarming. The British Attitudes Survey in 2000 found that only 16% of people trusted governments of any party to put the national interest above party political concerns - an all-time low. A Mori poll last year found that only a third of the public trusted government scientists to tell the truth about issues such as GM foods.

If the public doesn't believe what the government says, even when it tells the truth, its ability to do its job will be badly hit. Vast numbers of parents refused to believe government scientists' assurances that the MMR vaccine was safe, preferring to leave their children unvaccinated. The foreign secretary, Jack Straw, has acknowledged that even if weapons of mass destruction are ultimately found in Iraq, many would believe they had been planted.

Public scepticism is hardly likely to limit itself to the issue of Iraq. Take any contentious policy - the euro, asylum, ID cards, examination results - and see how the government fares against a growing tide of doubt about its motives and honesty. That trend cannot be easily reversed. But any serious attempt to do so must be based on a policy of openness, regardless of whether the facts are inconvenient or embarrassing.