John Browne, British Conservative member of parliament, said yesterday the new centrist alliance between Britain's Liberal Party and the recently formed Social Democratic Party (SDP) poses "a serious threat" to both the Right and the Left.

In Cambridge to deliver a talk on British politics and discuss defense with experts at the Kennedy School, Browne said in an interview that the alliance restricts Prime Minister Margaret Thatcher's government.

"Thatcher has personal charisma, but she doesn't have the instant star ability of a Muhammad Ali," Browne said, adding, "She can't easily put senior cabinet members into the House of Lords, because that would create threatening by-elections."

Browne, a 42-year-old backbencher from Winchester who specializes in economics and defense, said Thatcher's monetary policy will have to produce positive results by Britain's next general election if her party is to retain power.

"A lot of people underestimated the SDP," he said. "Its rise typifies the increasing volatility of politics in the West and Britain--the center is becoming credible."

Browne is a firm believer in monetary policy, but he noted that monetarism is designed to work in a free market. "The skew between the private and public sectors has widened," he said. "We've all been living for 30 years under socialism in Britain and have gotten used to the painkiller."

Monetarism, he contended, amounts to facing reality. "We were increasing taxes, increasing borrowing and then nationalizing industries. Everybody got hooked on the drug."

In a similar vein, Browne argued, this summer's riots in England arose because the participants "justifiably didn't have the courage to face reality."

Professionals

He cited the persistence of youth unemployment, racial and class tension, activities by "professional riot organizers," the decrepit condition of the inner cities and poor tactics by the British police as causes of the riots.

"It was ironic that our police made all the mistakes they could in London," Browne said, "when we've been very sophisticated in our riot control in Ulster for 13 years."

As a solution to the riots, Browne said "you just can't throw money at the problem. Wise management of the cities is needed."

Still, Browne said the "stern reality of monetarism does not compare with the real depravity of 1929 and 1930. The problem does not spring from money-- people were starving during the Depression, and no one rioted."

Browne said Britain had to build up its "technological base" to improve its economy and bolster its defense. "I believe in increasing interdependence, and peace above all. But peace through strength is the only answer to nuclear proliferation. Otherwise, we'll never have mutual respect."

On the touchy subject of Northern Ireland, Browne said Britain cannot abdicate its "responsibility.