But in a letter to Tony Blair, Labour's spokesman, Kenneth Clarke left open the possibility that MI5 operations could be extended from counter-terrorism to drug or fraud-related crime, if national security was threatened.
Mr Blair said last night that he was concerned about that loophole, left open by Mr Clarke.
He had raised the issue of MI5 activity after the Home Secretary had said in a BBC radio interview on 25 January: 'We need a Security Service to protect us against terrorism, to protect us against organised crime of a serious kind.' The Independent has also reported high-level police fears that MI5 had been emboldened by its success in taking charge of anti-terrorist activity, threatening to move into more traditional areas of police work.
But as Mr Blair pointed out, the Security Service Act 1989 precluded that, because it restricted MI5 to the defence of national security and safeguarding the economic well-being of the country against threats posed by people living outside the United Kingdom. In his letter, Mr Clarke confirmed that view, saying: 'The Security Service applies these criteria scrupulously.
'If, in the course of its work, the Service were to be given information relevant to the prevention or detection of serious crime, the Security Service Act allows the Service to pass that information to the police, or Customs and Excise, or other appropriate authority.
'But this is a very different matter from actually conducting investigations into such matters.' Having clarified the statutory and political position, however, the Home Secretary then injected a new uncertainty.
He said: 'Although I am concerned that the police, Customs and Excise and others concerned should be given all possible support in their work against fraud, drugs trafficking and organised crime, thankfully none of these activities takes place on such a scale as to constitute a threat to national security.
'I can therefore give you a clear assurance that while this assessment remains there will be no question of the Security Service undertaking investigations in such matters.' But as Mr Blair pointed out last night, the Home Secretary's reassurance had been carefully qualified. 'It all seems to depend on his assessment. We don't know what he will consider to be a threat to national security from organised crime, and how that assessment will be made.'
The letter also suggested that such an assessment would be made without reference to Parliament - without an amendment to the statute.
Mr Blair said he was writing to Mr Clarke to ask for assurances on those points and, at the very least, a commitment that if any change took place, a full report should be made to Parliament.
The importance of that was underlined by the Home Secretary, who stressed the essential secrecy of MI5 activity, and the rarity of his reply: 'Given the nature of the work of a Security Service, it is probably inevitable that there will from time to time be completely misleading and ill-founded assertions about the actions of that Service.
'In the main, there is little option but to remain silent in the face of such assertions. If we were to offer a response to certain claims, silence on any other occasion would be taken as confirming the truth of the claim then being made, however absurd that might be.'
Government denials that security agencies may have tapped telephone calls by members of the Royal Family were not enough. In such matters the public regarded ministers all too often as 'dupes or liars', a Tory peer said. Lord Marlesford's remark drew gasps and rumblings of disapproval from fellow peers, writes Stephen Goodwin.
Earl Ferrers, Minister of State at the Home Office, said: 'The Prime Minister has had categorical assurances from the heads of the agencies that they were not involved.'Reuse content