Protestant Ulster Unionist politicians today disrupted the British Parliament, vowed to bring local government in British-ruled Northern Ireland to a standstill and threatened to set up their own security force there following Saturday's assassination of a hard-line Unionist member of Parliament -- the Rev. Robert Bradford -- by Irish nationalist terrorists.

At the same time, police in Britain launched a massive around-the-clock search of hundreds of thousands of garages, businesses and abandoned houses for up to 500 pounds of explosives they believe have been hidden by Provisional Irish Republican Army terrorists responsible for four bombings in the past five weeks in the London area. The bombings have killed three people, injured 40 and destroyed the suburban London home of Britain's attorney general while he was out of the country.

The search in the London area alone, involving 16,000 police officers -- with all leaves canceled for the week it is expected to take -- was described by officials as the biggest ever mounted here. Large quantities of explosives were found by police in hiding places here during IRA bombing campaigns in London in 1972 and 1976.

In today's extraordinary disruption of Parliament, three hard-line Unionist members of Parliament led by the Rev. Ian Paisley were ordered out of the House of Commons and suspended for the next five business days after they repeatedly interrupted government statements on Bradford's killing with shouted accusations blaming Prime Minister Margaret Thatcher and her Northern Ireland secretary, James Prior, for the sharp rise in attacks by the provisional IRA in Northern Ireland, where four more Protestants, including Bradford, were killed last week alone.

Paisley and and two other members of Parliament from the Democratic Unionist Party in Belfast, Peter Robinson and John McQuade, sitting in a gallery overlooking the Commons chamber, shouted "rubbish" in response to Prior's call for calm in Northern Ireland. "You have given us nothing but the IRA -- you are guilty of it," McQuade shouted at Prior, whom hard-line Protestant Unionists have accused with Thatcher of giving Irish nationalist terrorists encouragement by improving British relations with the Republic of Ireland.

After the bewigged speaker of the House, George Thomas, failed to quiet the three with repeated calls of "Order, order," he suspended business for 10 minutes. As Thatcher, dressed in black as a tribute to Bradford, left the chamber, McQuade shouted at Thatcher, "There she is, the guilty woman. The blood of Ulster is on your hands."

Thomas won a voice vote of the house suspending the three Unionists from Parliament for five days for "grossly disorderly conduct and ignoring the authority of the chair," but they refused to leave. As members of all the other parties shouted up at the Unionists, "Out, out, out," Thomas ordered the sergeant-at-arms, Col. Peter Thorne, with his ceremonial sword dangling from his waist, to escort them from the chamber.

Outside, Paisley told reporters he would call on all Protestant Unionist politicians in Northern Ireland to refuse to cooperate with the government and to bring local functions to a standstill. "We can make Northern Ireland ungovernable and show to Mrs. Thatcher that she cannot govern except with the Protestant Unionist majority," he said.

"The situation in Northern Ireland is of such a serious nature," Paisley added, "that in order to bring it dramatically to the House of Commons and the people of the United Kingdom, my colleagues and myself felt we must demonstrate publicly today and place the blame on the shoulders of the government where we believe it belongs. No longer are we prepared to allow our people to be murdered and not do something about it."

Paisley has also promised to mount a mass demonstration of some kind against the government next Monday in Northern Ireland. He would not specify, but said it would be more than the hour-long protest strike throughout the province urged by Protestant Unionist leaders when Bradford is buried Wednesday.

Earlier today in Belfast, Paisley's rival as political leader of Ulster's Unionists, member of Parliament James Molyneaux of the Official Unionist Party, warned at a news conference that unless the British government could demonstrate improvements in security in Northern Ireland by Wednesday, the Unionists would form a force of its own. He, too, was vague about details. But he and another Official Unionist member of Parliament, Harold McCusker, told newsmen it would begin with establishment of an intelligence network reporting suspicious activities to the authorities.

They appeared to be asking for official recognition of such a network of Protestant Unionists, particularly in rural areas near the Irish border where Provisional IRA gunmen have been most active. McCusker said more Protestants in these areas could acquire permits to legally possess guns and defend themselves and their neighbors with them. Prior again urged Ulster Protestants not to "fall into the trap of reacting to the IRA." He said the terrorists "want a maximum amount of provocation and chaos to achieve their aims" of violently ending British rule of Northern Ireland.

But Molyneaux in Belfast demanded that Prior be fired. "The law-abiding people of Ulster have been brought to the boiling point by Mr. Prior's insulting request to keep calm while the IRA butcher us," he said.

In a message purportedly from its Dublin headquarters, the Provisional IRA said, in reference to its earlier accusations that Bradford had encouraged Protestant terrorists to murder members of Ulster's Catholic Irish nationalist minority, "armchair generals who whip up antinationalist murder gangs cannot expect to remain forever immune from the effects of their evil work. The IRA are commited to resisting British crown forces whenever and wherever possible."

Before helping cause today's disturbance in Parliament, Paisley said during a tribute to Bradford that more members of Parliament were likely to be killed before Christmas.