New rules on research and development. Looser consumer protection measures for utility consumers. Consideration of the future of the Rosyth dockyards. Cabinet arguments on the use of European regional funds. A review of ways to cut housing benefit. A plan to reform invalidity benefit. A possible reform of family policy. The potential for reductions in sick pay and pensions.

Each of these was the subject of one of the many Conservative Government documents that were leaked to Gordon Brown during the years that he served as an opposition frontbencher. It is a list the Metropolitan Police might have done well to consider before they barged their way into Damian Green's home and his parliamentary office, and held the Conservative politician under arrest for nine hours. It might have convinced them that such a course of action would be a mistake, and not a minor one either.

The police action against Mr Green was remarkable. It involved the deployment of force in numbers and heavy-handed intervention. Since such heavy-handedness was employed where a telephone call might have sufficed, one must conclude that the intimidatory tactics were deliberate. Perusing the list of Mr Brown's stories might have caused officers to reflect that by contrast with the extraordinary action they planned to take, Mr Green's was routine.

Members of Parliament frequently receive, and assist in the publication of, leaked documents. Mr Brown built his reputation partly on such activity, as have many others. It is vital that this be allowed to continue, and frightening that an attempt was made to stop it and to make a criminal out of an elected politician.

Civil servants who leak government documents should consider their own position carefully before doing so. They are employed to assist with the administration of public office and they should not lightly betray the confidences of those for whom they work. Nevertheless, there have been many occasions when the willingness of government employees to leak has been manifestly in the public interest. Perhaps the most famous is the way in which, in the 1930s, Winston Churchill was provided with briefing on Britain's poor preparation for a conflict in Europe.

Yet whatever the duties of civil servants, the duties of those receiving the information, whether they be MPs or journalists are quite different. Their role is to assist public debate and hold the Government to account. They should do this fearlessly, taking care only not to endanger the security of the nation.

Mr Green did not endanger the security of the nation, having, as far as is known, passed on only documents about immigration that might mildly embarrass the Government and cause useful questions to be asked about public policy. Using any kind of officer to search his house was therefore inappropriate, but deploying counter-terrorism officers was outrageous. The cavalier way in which the conduct of legitimate parliamentary activities was confused with terrorist ones poses serious questions about the use police will make of new powers to protect against terrorism.

A full account of how the police came to make this woeful decision is urgently required and should be demanded by the Prime Minister. After all, he should be the first to understand the value of the freedom Mr Green was exercising.