LONDON - Organizers of the London Olympics scrambled on Tuesday to assure a skeptical nation that a drastic shortfall in security personnel that has forced the deployment of military reinforcements would not compromise the safety of the Games, whose opening ceremony is less than two weeks away. Press Association, via Associated Press Nick Buckles, chief executive of the global security company G4S, appearing before a Parliament panel on Tuesday. He said his company's performance had been a "humiliating shambles." Andrew Winning/Reuters British troops touring the Olympic Park on Sunday. A shortfall in security personnel for the Games has forced the deployment of military reinforcements. But lawmakers who interrogated the head of the huge, global security company, G4S, which has failed to meet contractual obligations to secure a guaranteed security staff of 10,400, drew different conclusions, and even the chief executive himself, Nick Buckles, acknowledged that his company's performance had been a "humiliating shambles." Nicola Blackwood, a Conservative legislator on Parliament's Home Affairs select committee, which grilled Mr. Buckles for more than 90 minutes, said, "I had very little confidence in G4S fulfilling this contract before this session started, and now I don't have any confidence at all." For all that, Mr. Buckles said his company would not forfeit its management fee of about $90 million on a contract worth roughly $450 million because of work it had already done and would do in delivering security staff members. "I find that astonishing," said Keith Vaz, a lawmaker from the Labour opposition who is chairman of the parliamentary panel. With cabdrivers clogging central London in a protest against "Zil lanes" for the exclusive use of Olympics traffic, and newspaper stories about Olympic athletes from the United States and Australia who became lost in traffic, Games organizers and government ministers with their prestige at stake argued on Tuesday that tribulations in advance of the Games would fade as spectators focused on the ceremony and sporting contests opening on July 27. "I think this is not the moment for a blame game," said Jeremy Hunt, the government minister in charge of the Games. This is the time to pull together. Sebastian Coe, the chairman of the Games and a former gold medal-winning middle-distance runner, offered an equally positive view. "This is not a failure in numbers, we've got the numbers there," he said at a news conference. I think we'll get them to a good position, and at the moment that is the challenge, but let's put this in proportion. This has not, nor will it, impact on the safety and security of these Games. That of course is our No. 1 priority. Drivers of the capital's distinctive black taxicabs had their own priorities. More than 200 cabs converged on Parliament Square, honking horns in protest at the introduction of traffic lanes reserved for vehicles carrying athletes, Olympic officials and approved vehicles. "Taxis are excluded, which is unacceptable and wrong," said Jonathan Myers, head of a drivers" union. This is a working city and we need to get around and do our job. Because of the restricted traffic lanes, he said, "London is going to be gridlocked, and today we are showing them what it is like when it is gridlocked," he told the Press Association news agency, referring to lawmakers inside the nearby Parliament buildings. The prelude to the Games has been overshadowed by the admission last week by G4S that it would not be able to provide the promised number of security personnel, forcing the army to provide an extra 3,500 soldiers, some just back from the war in Afghanistan, bringing the total military numbers to around 17,000. Police forces in at least eight regions have also said they will provide officers to make up the shortfall. Mr. Buckles" appearance at the parliamentary committee subjected him to a remarkable and grueling interrogation during which he was forced to apologize, saying he was deeply sorry and blaming the failure of a scheduling system for the shortfall in security staff. Twice, David Winnick, a lawmaker from the Labour Party, asked Mr. Buckles whether his company's performance was a "humiliating shambles." "I cannot disagree with you," Mr. Buckles said. Mr. Winnick asked if his company's reputation was not in tatters. "At the moment, I would have to agree with you," Mr. Buckles said. Another Labour lawmaker, Bridget Phillipson, told the executive that his testimony left her with the feeling that he was "making it up as you go along."