Opposition parties have called for Mr Ishiba, widely seen as one of Prime Minister Yasuo Fukuda's most competent ministers, to resign over the accident in which the destroyer Atago collided with the fishing boat in crowded waters near Tokyo last Tuesday.

'One thing that I want to say is that we are not in any way dribbling out, hiding or manipulating information,' Mr Ishiba told public broadcaster NHK in one of three TV appearances on Sunday.

Asked if he would resign over the accident, Mr Ishiba said relatives of the victims had told him his responsibility was to find out the cause of the accident and prevent reoccurences.

'That is what is engraved most in my heart,' Mr Ishiba said. 'I must consider how to respond to their feelings, to the feelings of those with the bitterest thoughts, and I will decide myself how to do that.'

The accident has sparked outrage, partly because scant and seemingly conflicting information has prompted speculation of a possible cover-up and partly because of the strong streak of pacifism in Japan since the end of World War II.

The collision also comes at a time when Mr Fukuda's public support ratings have already slipped due to doubts about his leadership and public trust in defence officials has been dented by a bribery scandal involving a former top bureaucrat.

'The basic approach recommended for any organisation that has erred and wants to restore its public trust is to accurately grasp what happened and promptly make public a report on those findings,' said a weekend editorial in the Asahi newspaper.

'Yet, the response of the Self-Defence Forces (military) to Tuesday morning's collision ... shows a complete breakdown in upholding this essential tenet,' the paper said.

'Defence Minister Shigeru Ishiba bears a heavy responsibility in this incident.'

Japan's coast guard is investigating the cause of the collision, which occurred while the destroyer was on autopilot and soon after a change in the lookout crew.

Opposition Democratic Party leaders have suggested they might submit a censure motion against Mr Ishiba in Parliament's upper house, where they and smaller opposition parties have a majority.

The motion would be non-binding, but adoption of a similar resolution in 1998 forced the defence minister at the time to resign.

Japanese Cabinet ministers have resigned in the past over affairs in which they were not personally involved, while Mr Fukuda's predecessor, Mr Shinzo Abe, was weakened by the loss of several ministers over scandals and gaffes quitting last year.

'He (Ishiba) is trusted by the Americans and is clearly the right man for the position,' said Mr Brad Glosserman, executive director of Hawaii-based think-tank Pacific Forum CSIS.

'The question is, will the dictates of Japanese rituals take precedence over sheer capability?' -- REUTERS