As the national commission on terrorist attacks upon the United States began two days of hearings in the city, just one and a half miles from "ground zero", its panels' findings on the planning and emergency response set the stage for dramatic testimony.

Several current and former New York officials were due to testify, including the former New York mayor Rudolph Giuliani, and his successor, Michael Bloomberg.

"We want to know what mistakes were made and how to improve on those in the future," said the commissioner Timothy Roemer.

He said he expected one of the "most gut-wrenching and heart-pounding hearings" to date. "What I hope to learn and expect the hearings to produce is: what have we done since [the attacks]? Are we ready for the next emergency?"

The commission opened its hearing with a stark warning: "The details we will be presenting may be painful for you to see and hear." Within 20 minutes, families of the victims of the attacks were dabbing their eyes. More than 2,700 people were killed in the assaults on the twin towers.

Mr Giuliani had described the emergency work on that day as the "greatest rescue mission in the history of the United States".

But a 26-page staff report reconstructing events through first-person accounts revealed intense rivalry and lack of coordination between the police and fire departments.

Reportedly, a crush of radio traffic blotted out information and officials on the scene and emergency phone operators were unable to share what they knew. Competition between the fire and police departments meant the units considered themselves "operationally autonomous" and that they therefore failed to work together.

"This rivalry has been acknowledged by every witness we have asked about it," said the report read out at yesterday's public hearing.

While many of the safety procedures put in place after the 1993 attack on the World Trade Centre ensured some people in the towers did escape, others proved ineffective or possibly even dangerous when applied to the very different type of attack eight years later.

One survivor, Brian Clark, president of the Euro Brokers Relief Fund, said the public address system had advised: "Your attention please, ladies and gentlemen, building two is secure. There is no need to evacuate building two. If you are in the midst of evacuation, you may use the re-entry doors and the elevators to return to your office. Repeat, building two is secure."

Peter Hayden, a New York fire department assistant chief, told the commission that commanders on the scene quickly decided not to tackle the jet fuel-enhanced fire. "We determined very early on that this was going to be strictly a rescue mission. We were going to evacuate the building, get everybody out, and then we were going to get out."

But the commission's staff statement said: "The order was issued over a radio channel which could be heard only by officers on the Port Authority WTC command channel. There is no evidence that this order was communicated to officers in other Port Authority police commands or to members of other ... agencies."

New York city officials, meanwhile, highlighted a perceived "under resourcing" in the event of a further attack.

"The city of New York remains a high-risk target," said Frank Gribbon, of the New York city fire department. "We clearly have needs that exceed the allocations we've received."

Carolyn Maloney, a Democrat in Congress, said the city had "serious gaps in the equipment and training necessary to best prevent and respond to future terrorist attacks".