Alan Watkins: Once they have to wheel out the Official Secrets Act, it's the beginning of the end

The assistant is being prosecuted merely for being a conduit pipe

I t is a safe rule of politics that no prosecution under the Official Secrets Act ever does the government of the day much good. More than this: irrespective of whether it turns out to be successful or not, it either is a sign that the administration in question is on the slide or itself constitutes the beginning of that descent.

This was so even in the great days of the Cold War, when questions of freedom of expression were not at issue as they tend to be today, and when pieces of information were divulged by civil servants for cash on the nail. Harold Macmillan used to recall that a senior figure from MI5 would come to him and announce proudly:

"I say, Sir, we've just caught a spy," as if he were a dog bringing in some small, dead creature from the garden.

"Oh Lord," Macmillan would reply, "not another one. Can't you hush it all up somehow?"

"Afraid not, Sir. The legal boffins tell us it's gone too far already."

"But can't you see, man, that whenever you produce one of these spies, I get all the blame?"

And so he did. The expensive papers would produce solemn editorials along these lines:

"While the vigilance of the security services is to be commended, we cannot help noting that the clerk Carruthers, who was always in financial difficulties of one kind or another (and which should itself have sounded alarm bells with his superiors), was able unimpeded to spend 12 whole years supplying valuable information to his Russian masters ... lives lost ... need for inquiry ... highest level ... "

And so some eminent judge, usually Lord Radcliffe - the undisputed king of the committees - would be summoned to investigate the matter. Whenever they sent for Lord Radcliffe, you knew that the game was up. The name was like a knell. Indeed, one of his tribunals, on the spy William Vassall, marked the beginning of the end of Macmillan's government.

Two journalists were sent to jail for refusing to answer questions about their sources of information. The tribunal had been set up cynically by Macmillan as an instrument with which to beat Fleet Street. The imprisonment of the journalists made Fleet Street turn on Macmillan, who left office next year (his government remained intact).

The Vassall case - a spy case - produced consequences which were the same as those produced by the other category of Official Secret Acts case. This arises when an individual or a newspaper is prosecuted for obtaining or publishing information which the government would much prefer to be kept quiet. The al-Jazeera case is of this kind. It is due to be heard this week.

What seems to have happened is that a bright spark in Downing Street sent the transcript of a conversation between Mr Tony Blair and Mr George Bush to the research assistant of Mr Tony Clarke, an opponent of the Iraq war, then Labour MP for Northampton South. The talk took place in April 2004. It appears that Mr Bush raised the possibility of destroying the al-Jazeera television headquarters in Qatar (which, according to some versions, the President thought was in Iraq), but was dissuaded from following this course by Mr Blair.

Mr Clarke immediately sent the document back to No 10, saying subsequently: "After all, I am a special constable." In May 2005 Mr Clarke lost his seat. He was not charged under the Act, but his assistant and the original discloser are facing trial. Last week the Daily Mirror published part of the allegations.

The Attorney General, Lord Goldsmith, has threatened newspapers and broadcasters with prosecution under the Act if they reproduce what the Mirror has already disclosed. It does not seem that the paper itself - which consulted the Government before publication - is to be prosecuted. Unless Mr Clarke's assistant and his source were in cahoots, it does seem a little unfair that the assistant should be prosecuted merely for being a conduit pipe.

Though Mr Clarke's action was touchingly proper, it might have been more proper still if he had chosen to raise the matter on the floor of the House. While having an MP as a recipient does not protect a source against prosecution - as Mr Clive Ponting was to discover after leaking information about the sinking of the Belgrano to Mr Tam Dalyell - members are rightly accorded privileges which are denied to the rest of us.

The prewar threat to prosecute the Tory MP Duncan Sandys for receiving information on aircraft was the cause of trouble all round. The courts are wary of interfering in what are called proceedings in Parliament. But Mr Clarke did not elect to take this bold course. I like to think, perhaps vainly, that I should have done so if I had found myself in his position.

Lord Goldsmith does not have either public or political opinion on his side. Publish and be damned: that appears to be the popular view. Indeed, supporters of the Iraq war - or, at any rate, supporters of Mr Blair - should welcome evidence of that restraining influence over Washington to which the Prime Minister and his entourage frequently direct our admiring eyes.

In Mr Ponting's case, by contrast, the prosecution was seen as a contest between the Conservative government as embodied by Mr Michael Heseltine (then an untarnished figure, or relatively so) and the massed forces of dissent. When Mr Ponting was acquitted, the atmosphere in the lobbies was as if England had just lost the final Test and, with it, the series.

What did for the prosecution in this case was the learned judge's instruction that no distinction could be drawn between the interests of the state and the interests of the government. The jury simply refused to accept this. It was, plainly, a political prosecution; the jury declined to play the government's game. In the case of Ms Sarah Tisdall, however, the jury proved more amenable. In the comparable case of Ms Cathy Massiter, who supplied information about Mr Heseltine's surveillance of CND, no jury were given the chance because there was no prosecution; maybe because Ms Massiter was herself an MI5 officer.

The most political of all recent prosecutions was perhaps that of Mr Jonathan Aitken and others over the disclosure of information relating to the Biafra war. Though the case was tried in 1971, it was brought originally by a Labour Attorney, Elwyn Jones, to gratify the Nigerian government. Lord Goldsmith is now trying to please the Americans instead. Mr Aitken got off; his successors may do likewise.