London — When a British submarine sank the Argentine cruiser General Belgrano, the Sun newspaper here splashed across its front page one word: ''GOTCHA.''
When a BBC television program analyzed events in the war zone, an anchorman referred to British ''claims'' as well as Argentine ones. Another interviewed critics of British strategy along with supporters.
Both kinds of reporting about the Falklands crisis - the first hotly emotional, the second dispassionate and cool - are at the center of a fierce battle here at home. It raises basic issues about how a shooting war is to be reported in the mass media age, and the responsibilities of government and media alike.
Critics of the BBC are throwing around the world ''traitorous'' to describe its attempt at unbiased reporting. Those on the political right, including retired admirals and die-hard conservatives and Prime Minister Margaret Thatcher herself, want the BBC to be more biased - in favor of the government.
Those on the left such as the Labour Party's Tony Benn, attack the BBC for the opposite reason - for allegedly being a government mouthpiece. The more traditional British left is outraged at right-wing mass tabloid newspapers such as the Sun, the Star, and the Daily Mail, and accuses them of jingoistic and dangerous simplicity and amorality.
Meanwhile, the press itself is mounting a strong attack on the British Ministry of Defense for ''losing the propaganda war'' to Argentina by heavy and multilayered censorship, and by failing to provide facilities for television pictures to be transmitted back to Britain from the war zone.
No British TV film from South Georgia or the Falklands exclusion zone were seen for the first three weeks of the hostilities. At this writing, the first film was due in Britain by ship on May 13.
Privately, some government sources here concede the Defense Ministry has done badly. The British are wrestling with some of the same issues that faced former Presidents Johnson and Nixon, and the US media and people, during the war in Vietnam.
When is reporting objective and when is it biased? One man's reasonableness is another man's treason.
The harsh public debate here illustrates the impact that the prolonged crisis is having on Britain with traditional political enmities coming to the fore. The Labour Party is seizing the chance to lambaste the Sun owned by right-wing Australian Rupert Murdoch, and the Star as well, because of their anti-left sentiments in general.
Conservatives tend to see the BBC as a nest of left-wingers with questionable loyalty to Tory (Conservative Party) governments. A group of Conservative members of Parliament have tabled a motion in the House of Commons accusing the BBC of being ''loftily neutral.'' A former Conservative minister, Mrs. Sally Oppenheim, called a recent BBC television program an ''odious and subversive travesty.''
The London Times (another Murdoch paper) and the Daily Telegraph have been right wing in supporting Mrs. Thatcher. The Guardian and the Financial Times have stressed diplomacy more.
Labour leader Michael Foot called the Sun and the Star ''hysterical'' in the House of Commons May 11. There is little doubt that the right-wing tabloids have been excessively warlike and sensational, with headlines such as ''Give 'Em Hell'' and ''In We Go.''
Only two days after Argentina occupied the Falklands, the Sun headlines, ''It's War.'' The sensationalist Sunday Paper News of The World, also owned by Rupert Murdoch, treated the war as a sports event, shouting in a headline, ''Latest Score: Britain 6, Argentina Zero.''
On the first day of the crisis, the Star ignored diplomacy and wrote in an editorial: ''Britain must throw the invading Argentines into the sea because the Falklands are British, just as much as Aintree Racecourse.'' When Tony Benn and nine other Labour members urged that the task force be stopped, the Sun asked on its front page, ''Whose Side Are They On?''
The newspaper hired a lawyer whom it quoted as saying that Mr. Benn was ''preaching something very like treason.''