Foreign Minister David Owen has been the target of a sustained, scathing attack from the largely Conservative press here because he has refused to imitate Washington and let Premier Ian Smith of Rhodesia visit Britain.

The 10-day onslaught reached a climax of sorts yesterday when a contributor to the editorial page of the Times of London called Owen "the first obstacle to peace."

But this was mild compared to the blasts from Conservative tabloids. The Sun charged Owen and the Labor government with pursuing "a hysterical vendetta" against Smith. The Daily Express accused Owen of "fatuous, little-minded spite" and ridiculed the handsome foreign secretary as "light comedy's loss to politics."

All this helped anger Conservatives meeting at their annual conference in Brighton yesterday. They even booed their own foreign affairs spokesman, John Davies, although he delivered a stiff attack on the government.

Davies drew fire for insisting that Britain could not defy the United Nations and singlehandely lift sanctions on trade with Smith's white-dominated government. A motion to give Davis a vote of thanks, was shouted down.

The passion generated on Smith's behalf has left Owen and the government here unmoved, and Smith will still not be allowed in. Those close to Owen say he is not a bit embarrassed by Smith's visit to Washington and regards the visit chiefly as an episode in domestic U.S. politics rather than diplomacy.

When Secretary of State Cyrus Vance first told Owen that there was pressure to let Smith in, Owen is said to have replied: "You know your congressional situation best."

The issue of a visa for the Rhodesian leader also must be seen against the background of his unilateral declaration in 1965 of independence for Rhodesia, till then a British colony. The break came over very much the same issue that keeps Rhodesia in the headlines today: black majority rule.

Domestic politics plays some part, too, in Owen's refusal of a visa. If he is to achieve his ambition and become leader of the Labor Party, he must allay the suspicions of the Labor left-wingers.

Owen's men say that the foreign secretary also has sound diplomatic reasons for keeping Smith out. The most important is that London has abandoned hope of making Smith agree to the Anglo-American people plan.

The key point of the plan are putting a U.N. presence into Rhodesia: integrating the guerrilla forces of the Patriotic Front with Smith's army and placing the armed forces under Lord Carver, the former British army chief. Control of the guns during a transition period until elections has always been at the heart of the Rhodesian quarrel.

A Smith visit here, it was feared, would also produce an emotional propaganda outcry, with the Rhodesian prime minister appealing to "kith and kin," white relatives of Rhodesians in Britain, for support.

Finally, the Foreign Office regards Smith as a fading force in Rhodesia and fears the climatic struggle will be waged between the rival groups in the Patriotic Front. A visa for Smith, it is said, would exaggerate the importance of his role.

But none of these reasons have impressed Conservative newspapers here. The Daily Mail accused Owen of "legalistic claptrap" and added, "We do not reufse entry to black tribal chiefs, cunning or unscrupulous though they may be."