Weak trade fleet adds to British economic woes

The persistent slump in world trade and fierce international competition is continuing to have a serious effect on Britain's once-leading merchant-navy fleet.

United Kingdom-owned vessels fell to an all-time record low registration of 913 ships in December, down from a figure of 994 at the start of 1982. The loss of 81 ships last year to the scrapyards or permanent berths is of deep concern to the British government and may soon bring about some kind of state intervention to help one of the country's most seriously declining commercial undertakings.

Britain has scrapped or laid up 700 cargo ships since 1975, a drop in carrying capacity from 50 million tons to 26.9 million tons.

Hundreds of merchant-navy officers and seamen from some of the country's principal shipping companies have joined many other mariners in looking for jobs.

Britain's shrinking merchant fleet is also having a very bad effect on the nation's overseas earnings.

With 26 percent of tankers and 11 percent of the world's cargo ships laid up, the U.K. has particularly suffered from the international shipping recession.

Many international competitors receive subsidies to build ships for general-cargo carrying, but the Thatcher government has resisted this policy of state help.

Some British ships have been reregistered abroad under ''flags of convenience ,'' a policy that has threatened maritime safety standards and cost many U.K. seamen their jobs.

The National Union of Seamen and the Merchant Navy Officer's Association have urged the government to follow Norway and only allow British support vessels - Norway excludes all foreign flags - to operate in its North Sea oilfields.

Union officials claim that 2,000 U.K. seamen could obtain jobs in North Sea activities if Britain adopted a ''Union Jack'' rule. At present 50 percent of the support ships operating in the North Sea are foreign.

British shipowners see little prospect of any increased trade within the next few years. There is also concern that the alarming decline in Britain's once-powerful steel industry will lead to more U.K. ships being built abroad and operated from ''flags of convenience'' countries.

The third world countries that used to be substantially dependent on Britain's large merchant fleet for imports and exports, have increasingly switched to owning African- or Asian-registered vessels.