British lawmakers say it is time to overhaul the quaint, 15th century security procedures in parliament following two embarrassing intrusions there this week, and a revelation that al-Qaida terrorists had a plot to target the building.

Senior British officials are expressing concern about safety inside London's Palace of Westminster, venue of the House of Commons and the House of Lords, after intrusions this week by protesters and a newsman revealed huge security gaps.

On Wednesday, several fox hunting supporters got onto the floor of the Commons after entering the building by posing as construction workers.

The protesters were eventually wrestled down by sword-bearing guards dressed in knee-length stockings, black frock coats and silver-buckled shoes, the same style of uniform they've worn since 1415.

Then on Thursday night, the Sun newspaper published an article by an undercover reporter who smuggled a fake bomb into parliament while posing as a catering service waiter.

British Home Secretary David Blunkett says the security breaches are unacceptable.

"We now need not medievalism, but modernity," he said. "We need to be in the 21st century in tackling the potential for suicide bombers and the risk we're at. And that means a director of security for the whole of the Palace of Westminster."

Adding to the concern is the revelation by the leader of the Commons, Peter Hain, that al-Qaida has been eyeing parliament for an attack, as he explained on British radio.

"The security service briefed me some time ago about intelligence that they had about al-Qaida operatives in Britain focusing on parliament," he said. "When I was briefed and I probed and I spoke to the director general about that intelligence, I was very determined to act upon it."

Not all lawmakers are ready to throw out parliament's ancient traditions. Among them is Derek Taylor of the opposition Conservative party.

"I think some are trying to use this as a means of getting rid of the sergeant-at-arms and the role that he has," said Mr. Taylor. "I think they are absolutely wrong. I don't think they should act precipitously on this. They should think very carefully about it and not risk centuries of tradition for the sake of a publicity stunt."

The managing editor of the Sun, Graham Dudman, says his paper's investigation should raise alarms.

"This wasn't a publicity stunt," he said. "This was a major investigation and we've done the House of Commons a favor. We've done a favor in exposing what is a truly, truly terrifying breach of security at the House of Commons."

This week's incidents are the latest in a string of security failures in and around parliament during the last six months. In March, environmental activists scaled the Big Ben clock tower that overlooks parliament. And in May, fathers' rights protesters threw flour at Prime Minister Tony Blair as he spoke in the Commons.

Despite the latest lapses, no one is predicting a quick fix. Leaders of the Commons and the Lords would have to agree on any security changes. London's fabled Scotland Yard police force cannot help, as tradition bars it from entering the building. And most lawmakers want to avoid any measures that would interfere with their constituents' time-honored access to Westminster.