Britain rules fewer waves than it used to

Britain will never again be able to win a war of the Falklands type. The Royal Navy will be too small and the capabilities of British warplanes will be too limited.

These are the only sure conclusions arising from a furious British debate about the effectiveness of Britain's Navy sparked off by an editorial in the authoritative annual review Jane's Fighting Ships.

An article, by Jane's editor, Capt. John Moore, accuses the British government of ''emasculating'' the Royal Navy and, on grounds of economy, robbing it of the capacity to be a rounded seaborne fighting force.

So severe was Moore's criticism that the Ministry of Defense has issued an unprecedented rebuttal of his main arguments.

For good measure, a former defense secretary, Sir John Nott, who framed the 1981 cut-backs in the Royal Navy and then six months later headed the Defense Ministry during last year's Falklands conflict against Argentina, weighed in with a counterattack of his own.

Moore provoked the argument by declaring that two years ago the Thatcher government showed a ''lamentable failure'' to appreciate the role of seapower in affairs of state. The war in the South Atlantic, Moore claimed, showed the British fleet defective in early warning of air attack. There was also a severe shortage of air cover against attacks by fighter bombers.

These threats, he said, had been ignored for at least the past 15 years. He said there were also shortages of submarines, defenses against mines sown by an enemy, and ships capable of carrying short takeoff jets of the Harrier type.

The Jane's review is regarded worldwide as a well-informed register of naval strengths. The Moore editorial, one of several in recent years to have taken a critical line on government naval policy, is seen in Whitehall as potentially damaging to the credibility of the Royal Navy in possible future conflicts.

Responding to the Jane's attack on his cost-cutting policies, Sir John Nott, who has now retired from active politics, conceded that having a fully rounded fleet is no longer within Britain's financial capacity.

''The Navy was overprogrammed. Its plans were too ambitious,'' he said. ''We must decide our priorities. The Royal Navy will not decide those priorities for itself, they will have to be imposed.''

Moore's arguments are widely accepted by old sea dogs, of whom he is one, but contested by Thatcherite ministers who argue that a distinction has to be drawn between what the Royal Navy needs and what governments can afford to supply it in the way of modern equipment.