The British magazine New Statesman has accused the U.S. National Security Agency of using a secret telecommunications center in northern England to tap telephone and telex communications throughout Europe with the help of the British government.

The monitoring is carried out on a large scale with the aid of computers as NSA's 800-employee Menwith Hill station in the Yorkshire moors, according to the New Statesman, which calls the station the largest civilian surveillance post maintained outside the United States by NSA, the intelligence agency for the United States military.

The weekly magazine, which in recent years has added aggressive investigative reporting to its left-wing political commentary, also accuses Britain's Post Office, which runs the telephone system here, of providing NSA with possibly illegal access in international communications in and out of Britain through its microwave radio relay system.

The British Defense Ministry has denied that NSA uses the Menwith Hill station to monitor telephone calls inside Britain or calls between Britain and the United States. But the New Statesman pointed out that these denials do not cover telex or telegram traffic, telephone calls between Europe and Britain or between Europe and the United States through Britain.

British officials describe Menwith Hill as a NSA communications relay station for "rapid and secure communications" between United States military installations abroad and the United States via satellites and other means.

American officials here said they would maintain their policy of not discussing any security installation such as the NSA station at Menwith Hill, referring reporters to British officials instead.

The New Statesman report, written by Duncan Campbell and Linda Melvern, is part of an extended investigation by Cambpell of wiretapping and other surveillance in Britain and bases its claims on unnamed sources in the British and American intelligence communities and on circumstantial evidence about the Menwith Hill station.

The story noted in detail the tight security and great secrecy surrounding the base, its space-age satellite communication aerials, receiving dishes and protective domes, its sophisticated computer and communications equipment in massive concrete blockhouses and its close proximity to an apparent interconnection with a tall relay tower in Britain's microwave telecommunications systems.

The story concluded that NSA employes at Menwith Hill, working round the clock, use computers to sift through "the communications of private citizens, corporations and governments for information of political or economic value to the U.S. intelligence community."

This work is so secret, the story alleged, that most of the American employes live on the 562-acre base and must report to a security officer their contacts with British nationals outside it.

The Americans actually are somewhat more integrated than that and many live in the surrounding communities, where they are known for their friendliness and for the fact they never discuss their work.

As the New Statesman noted, American intelligence officials acknowledged during 1975 congressional hearings that all transatlantic communications by air or cable could be intercepted, and there have been previous reports of international communications being monitored here by the American military in cooperation with the British.

Earlier this year, Campbell accurately described the location and function of a telephone facility in London used by British police and security agencies to monitor "thousands of calls" within Britain in an operation codenamed "Tinkerbell."

A subsequent government report made by the Home Secretary claimed that he had issued only 467 new warrants for telephone tapping last year. But each warrant, the contents of which are kept secret, apparently covers the subject of what could be a large number of individual taps. Campbell has alleged that many other wiretaps by security agencies are not covered by warrants.

In respone to a political and media pressure following a series of New Statesman articles by Campbell, the government appointed a senior appellate judge to review and report further on the wiretap warrant process.

This has not satisfied critics, however, including the 125,000-member Post Office Engineering Union, which has made its own report on "tapping the telephone," in which some of its members have indicated being involved. The union's report criticizes the government inquiry for being too narrowly based, leaving out surveillance by British security forces in Northern Ireland and unsanctioned wiretapping and calls for legislation to protect the British public from "potentially enormous" wiretap abuses.

Campbell, 27, who has specialized in investigative reporting on electronic surveillance for several years, was hired by the New Statesman after Australian journalist Bruce Page became its editor two years ago. Page has tried to revive the 70-year-old political journal's circulation and influence with investigative reporting seldom found in British magazines or newpapers, except the Sunday Times, where Page had previously been head of its investigative Insight team.

Campbell, who has a degree in physics from Oxford University, was unsuccessfully prosecuted several years ago for allegedly violating Britain's Official Secrets Act by his inquiries into government surveillance. Campbell said most of his information actually comes from technical information in public records about Britain's communication systems.