An unprecedented battle between two British seats of national influence, Buckingham Palace and Downing Street, went into its third week today showing no signs of abatement.

The issue on which combat initially was joined, reported political disagreement between Queen Elizabeth II and Prime Minister Margaret Thatcher over sanctions against South Africa, now has receded into the background. Current national interest is focused on an unseemly skirmish between the palace and a London newspaper, the Sunday Times, over whether the queen has any political views at all, and whether she or any of her advisers is entitled to express them.

Parliamentary activists today called for the queen's longtime press secretary, Michael Shea, to resign after it was acknowledged that he was the palace "mole" whose briefing of a Sunday Times reporter resulted in a July 20 story headlined "Queen Dismayed by 'Uncaring' Thatcher."

But senior palace officials, in a rare counteroffensive, have accused the newspaper of distorting the story. In his briefing, the palace has said, Shea "said nothing which could reasonably bear the interpretation put upon it" by the Sunday Times.

The controversy began in mid-July, when numerous local newspapers simultaneously reported that the queen was concerned over schisms in the Commonwealth, the organization of Britain and its former colonies that she ceremonially heads. Thatcher's refusal to consider punitive measures against Pretoria had put her at odds with the vast majority of the 49 Commonwealth members.

The stories, apparently the result of briefings by leaders in Thatcher's Conservative Party who sought to pressure her by invoking the queen's displeasure, set off a media race for more explosive insights into the sovereign's political views.

Although the British monarchy serves as the highly respected symbol of national unity, the royal family is presumed to be uninvolved in politics, and to adapt its views to the government of the day.

In its July 20 story, however, the Sunday Times, quoting unnamed "senior advisers" and confidants of the queen, said she not only was upset about the sanctions issue, but disapproved of Thatcher's policies on a range of subjects -- from the crackdown on trade unions, to Britain's assistance in the U.S. military raid against Libya.

It was suggested, in this and subsequent articles, that the queen's political beliefs could be compared more closely with those of the Social Democratic Party, a slightly left-of-center grouping, than with the Conservatives.

Initially, the palace confined itself to denouncing the Sunday Times story as "without foundation." This week, however, as other media outlets strived to discover the "mole" and top the Sunday Times account, the queen's advisers struck back.

In a letter yesterday to the Sunday Times' sister publication, The Times, the queen's private secretary, Michael Heseltine, said it was "axiomatic" that "whatever personal opinions the sovereign may hold or may have expressed to her government, she is bound to accept and act on the advice of her ministers."

"After 34 years of unvarying adherence to these constitutional principles," he wrote, "it is preposterous to suggest that her majesty might suddenly depart from them. No sensible person would give a moment's credence to such a proposition."

Besides, Heseltine said, no member of the royal household would reveal any such personal views to the press even if he or she "knew what her majesty's opinions on government policy might be (and the press secretary certainly does not)."

Thus, while denying that he knew anything to leak, the palace identified Press Secretary Shea as the much-sought mole.

In today's episode of the deepening drama, as strict constitutionalists were calling for Shea's scalp, Sunday Times Editor Andrew Neil again entered the fray.

If Shea did not know anything about what the queen thinks, he asked in his own letter to The Times, "why was he briefing us at all . . . he is the official voice of the queen and newspapers have always worked on the premise that he speaks authoritatively about her."