The government today ordered two more British firms to ignore the U.S. ban on equipment for the Siberian natural gas pipeline, a stiff rejoinder to the Reagan administration's imposition of sanctions against a Glasgow company that shipped a load of turbines yesterday.

The British retaliation was accompanied by a statement that said the Thatcher government has "no wish to escalate the dispute, but in the absence of a mutually acceptable solution is determined to defend the United Kingdom's national interest." Officials let it be known that Prime Minister Margaret Thatcher personally was displeased over the U.S. action against Britain, which considers itself a close and faithful ally of Washington.

The two companies, subsidiaries of American firms, have contracts worth about $17 million for firefighting equipment and radio antennas to be used at sites along the pipeline construction route. Four other British companies including John Brown Engineering Ltd., the firm blacklisted yesterday by the Commerce Department, are already under orders to ignore the embargo.

By acting today, within hours of the John Brown sanctions announcement in Washington, Britain was underscoring its frustration with the Reagan administration's stance on the pipeline issue.

In the past week, top British officials, including Thatcher, have met with visiting Defense Secretary Caspar W. Weinberger and trade negotiator William Brock. In those sessions, sources said, the Americans have expressed "contradictory" sentiments, on the one hand affirming the strength of Anglo-American friendship and a need to resolve the pipeline dispute, and on the other hand saying that sanctions for defiance of the president's ban must go ahead.

Yesterday, Defense Minister John Nott, declaring that the United States is Britain's "greatest ally," announced that servicing of the Trident nuclear missiles being purchased from the United States would take place in Georgia instead of in Scotland as earlier forecast. This is a symbolic strengthening of the nuclear link between the two countries but also represents a loss of jobs that had been promised for construction of the servicing facility.

Today, politicians of all parties expressed anger at the government's willingness to defer to U.S. nuclear leadership at the same time that the Reagan administration is punishing a British company for fulfilling a contract with the Soviets. One member of Thatcher's own Conservative party called the combined actions "totally unacceptable."

In a speech today in Copenhagen, Foreign Minister Francis Pym called for a European-American meeting to resolve the pipeline differences. Such a session has been put off because of disagreement among the four European countries involved -- France, West Germany and Italy as well as Britain -- over what measures would persuade Reagan to drop his embargo on pipeline contracts in which American parts, licenses or subsidiaries are involved.

The two companies affected by today's order to ignore the ban are Walter Kidde, manufacturer of the firefighting equipment, and Andrew Corp., which makes radio antennas.

John Brown officials said today they had been served the U.S. Commerce Department's prohibition on exports of gas- and oil-related goods. But they said the company intends to go ahead with the manufacture and delivery of the remaining turbines purchased by the Soviets.

The government's statement extending its order aginst the Reagan embargo said efforts would be continued "to persuade the U.S." to rescind the sanctions on John Brown and reverse its policy.