THREE hundred shipping companies, including some based in Hongkong, have agreed to new standards of maintenance and emergency planning designed to make the ''astounding'' mistakes of skippers a thing of the past. The move coincidentally follows public outcry over recent disasters like the tanker Braer off the Shetlands north of Scotland and the recent major tanker disaster off the north coast of Spain. But it is also prompted by the fact that spilling as little as a barrel of oil in a California port can now cost US$1 million in damages. The companies have acted together to try to reduce rocketing insurance premiums after what they admit have been appalling lapses. They concede that a lack of adequate return on their investment during the 1980s has meant the world's merchant fleet is now ageing, ill-maintained, and has poorly equipped crews. Incidents have reached such a peak that insurance costs have doubled since 1989. The companies which run their own mutual insurance organisation, the Standard Club, have already shed 25 per cent of their members who were considered too high a risk. Now the club, which includes big groups like John Swire, P & O, Furness Withy and Smit International, will insist that all the 3,000 ships, from large tankers to ferries, operated by member companies meet the new standards. Mr Charles Mawdsley, claims director for the club, said some incidents were ''unbelievable'' - tramp steamers entering ports without the right charts and running aground, officers failing to notice oil spilling into harbours when refuelling, officers of the watch disappearing into the chart-room while their vessels were on auto-pilot, then colliding with fishing vessels. While the vast majority of incidents involved human error, there are no comprehensively globally applicable operating standards for vessels. The companies in the Standard club estimate that 25 per cent of their members do not have any written operating procedures. ''They conclude that it is the master's job to run the ship, not the owner's responsibility when it is outside port,'' said Mr Mawdsley. Mr Karl Timmermann of P & O Bulk Shipping, said: ''Never have standards of crewing been lower. The industry now realises it has got to get its house in order.'' The new procedures will force ship operators to bring in written safety policies, with full audits of each vessel, and have a safety officer on board. Ships insured by the club will need to have and operate full maintenance schedules, rather than just react to problems as they occur. ''Without doubt maintenance schedules were pared to the bone in the mid-1980s and are probably still being pared today,'' said Mr Mawdsley. The head surveyor for the club, Mr Eric Murdoch, commented: ''If you do find the cause of the Braer disaster you will find somewhere a procedural error.'' The majority of crews are now hired through manning agents. Under the new rules at least four officers will have to be permanently employed by a company and the top four officers will all have to be of the same nationality so communications problems are minimised. Companies will be told to avoid the random mixing of crews of different nationalities.