London — Why should the British public have the right to know more about what its politicians and civil servants are doing? ''Because,'' says Des Wilson, chairman of a freedom of information committee to be launched in January, ''secrecy creates a great deal of paranoia about what government is actually doing.
Prof. James Cornford, who is also associated with the new campaign, says, ''People have the right to know the reasons and the data and the statistics used by policymakers to reach their decisions.''
Campaigners say it is right to withhold information that could endanger national security. But why, asks Professor Cornford, are patients who go to a National Health Service doctor forbidden to see notes written by that doctor on the state of their health?
The reason, the professor says, is that the notes technically belong to the minister of health. They are state (and crown) property. Under a series of laws and statutes, they are classified - unavailable to the patient, although they can be requested by other government departments such as the police.
The British Medical Association is deeply concerned. Under a new data protection bill that is about to be enacted by the House of Commons, much computerized data on individuals is to be safeguarded by law. But handwritten data is not included.
Doctors say the Ministry of Health could not prevent police obtaining patient records in the case of rape or other assaults, even if the patients themselves wanted privacy.
Mr. Wilson, also chairman of the Friends of the Earth U.K. environmental lobby, says some secrecy in Britain is laughable.
''All water board meetings in this country are closed to the press by a new law passed this year,'' Mr. Wilson said in an interview. (The government argued that excluding the press would ''facilitate decisionmaking,'' a view rejected by the Guild of British Newspaper Editors, which sees water rates and shortages as a vital national concern.)
''So picture the scene in the Kremlin. Yuri Andropov is sitting there and his top spy in Britain comes in. 'Comrade,' the spy says, 'I have a map showing where all the British nuclear forces are located.'
'' 'That's nothing,' says Andropov. 'I've got the minutes of the Leeds water board here!' ''
Peter Hennessy, Whitehall (civil service) correspondent for the Times of London newspaper, recalls an essay by William Clark, press secretary at the British Embassy in Washington at the end of World War II.
Mr. Clark told of being asked by a new embassy political chief to sign a paper acknowledging that he had been made aware of the Official Secrets Act. The political chief explained that Clark could not divulge information to ''people who might make use of it.''
The new chief just happened to be Donald Maclean - who later defected to Moscow after years as a spy for the Soviets within the British Foreign Service.
Meanwhile, Mr. Wilson believes that making more information available to the public could actually help the government.
He has just lobbied, successfully, to force the government to agree to introduce lead-free gasoline into Britain.
During his campaign, the U.K., West Germany, and the Netherlands submitted a joint memorandum to the EEC Council of Environment Ministers on the issue. In Britain, the memo was routinely classified as secret, in accordance with civil service rules.
It was leaked to Mr. Wilson, who published it in the journal of his lobby group Clear (the Campaign for Lead-free Air).
''We were pleasantly surprised,'' he told me. ''It was mostly unambiguous, and contained . . . a reasonable note of urgency. . . .''
Although the campaigners want legislation supporting the public's right of access to nonsecurity, nondamaging government data, they are prepared to settle for smaller goals while the Thatcher government dominates the House of Commons.
Another possibility for the new campaigners: a serious, sustained lobbying effort to tack onto individual bills going through Parliament clauses requiring public disclosure.
''What's needed for a breakthrough,'' London Times reporter Peter Hennessy says, ''is a consumer issue, on which the government has written a spectacular report, which is then leaked to a newspaper bit by bit.
The biggest case to date was the Sunday Times's campaign years ago against a company that produced the drug thalidomide. The newspaper refused to abide by legal rules and published details of how the drug, taken by expectant mothers, had led to deformities in babies.
Campaigners now hope for a case that strikes more directly at government secrecy, just as the original Freedom of Information Act in Washington in 1966 arose from a protest by veterans who wanted more information from the Veterans Administration.