This newspaper felt the sharp edge of the Prime Minister's tongue yesterday for reporting that a United States senator had denied that National Party leader Don Brash told a senatorial delegation National would scrap the ban on nuclear-propelled ships by lunchtime. This she labelled "attack journalism".

If she meant aggressive journalism, we plead guilty; if she meant it was antagonistic to her, she is mistaken. The issue of what Dr Brash said, or did not say, to the senators in January has been festering in politics for a fortnight. It began when Helen Clark, quite improperly in our view, made public some of the contents of a note made by an officer of the Ministry of Foreign Affairs and Trade about a conversation between the senators and National members of Parliament.

Twice last week she said Dr Brash told them that if it was up to him the anti-nuclear legislation would "gone by lunchtime". Dr Brash said he could not remember. The Herald contacted one of the delegation, Senator Don Nickles. He said he did not recall Dr Brash saying any such thing. He did say that National did not give the delegation any assurances that the ban on nuclear-propelled ships would be eased. Yesterday on National Radio a second senator, Gordon Smith, questioned the Government's account of the meeting. More attack journalism?

The Herald went to some trouble to clarify this point because two important consideration are at stake: National's attitude to the nuclear policy, and the credibility of its leader. Publicly Dr Brash has been denying that National would do away with the ban unless it had a public mandate. If he had been telling foreigners something different in private it would be a matter of public concern.

Yesterday, the Government returned to the subject. Foreign Minister Phil Goff released part of the ministry note on Dr Brash's conversation. It states: "Dr Brash made the throwaway comment, 'If the National Party was in government today, we would get rid of the nuclear propulsion section today - by lunchtime even'."

Does that conflict with Senator Nickles' recollection that they received no assurances the ban would be eased? The official interpreted the statement as a "throwaway comment". The Americans did not take it as any sort of assurance. Yet the Government characterised it differently this week.

Far from scoring a telling blow against Dr Brash, the Government has simply compounded its original offence of bringing the contents of a confidential memorandum to public attention. It is a thoroughly good thing that the Foreign Ministry's officers attend meetings that leading Opposition members may have with visiting representatives. It is in the country's interest that those who make up its next Government are well briefed, do not leave wrong impressions about their intentions and avoid commitments they might be unable to keep.

Opposition leaders, however, will not make use of the service if the officials' reports are going to be used by the Government for political purposes. There is no way the ministry can prevent that; it has to serve the Government of the day. We rely on ministers to abide by the conventions and resist the temptation to exploit their access to such material, even when they think it discredits their opponents' public position.

Clearly the Government is anxious to move the focus off Maori issues, where National is making such headway, and onto areas where National's likely position will be less popular. Nuclear policy is ever Labour's fall-back; in trouble it invokes the bomb.

Inconveniently for Labour, and unfortunately for the country in our view, National under Dr Brash looks likely to keep the anti-nuclear policy in force, if not in legislation. This, we have said, is neither responsible nor credible, but at least we have learned from the US delegation that National did not leave the senators with a different impression. It was good of them to say so.