Safety experts were ridiculed and abused when they refused to sign off proposals for a new stadium at Casement Park, a Stormont committee has heard.
Laura Strong, from the Safety Technical Group, said she was left "shaken" after a meeting with the GAA, their English-based design team and government officials in June 2014.
She said: "What we were subjected to was ridicule, abuse, (we) felt patronised and considered that efforts were being made to humiliate us."
Approval for the GAA's 38,000 capacity stadium in West Belfast - a proposed venue for Ireland's 2023 rugby World Cup bid - was overturned in the High Court last December when residents won a legal challenge to block the plans.
Ms Strong was appearing before Stormont's Culture Arts and Leisure s crutiny committee alongside senior safety officer Paul Scott, who previously told MLAs he felt bullied into dropping objections to the new ground.
The 2014 meeting was convened at a south Belfast hotel to discuss emergency evacuation arrangements at the site.
Ms Strong said she was "taken aback" by the tone of the discussion.
"This meeting took on a whole other context," she added. " Health and safety people are not very popular. But, on this occasion I felt that we were being made to feel belittled.
"I certainly, in my career had not experienced a meeting like that in the past.
"This was over and above anything that we should have had to deal with in our role. People were openly laughing at us."
Later, two GAA officials apologised for the behaviour directed towards the safety officers, it was claimed.
MLAs were told the plans did not meet health and safety requirements to evacuate the Andersonstown Road stadium within eight minutes.
Mr Scott said global research has established that crowds start to panic after eight minutes.
He said: "The big fear is panic and crushing. People, after eight minutes, tend to worry and panic therefore there should be appropriate exits for them to leave to a place of relative safety."
Casement Park exits could not cope if there was a capacity crowd, the committee was told.
There could also be further difficulties because the site, which is surrounded by houses, is serviced by only one main arterial route.
Mr Scott added: "This is a challenging site. It is not insurmountable but it is going to be challenging."
More than £67 million of public money has been set aside for the Casement Park expansion as part of a Government commitment to upgrade outdated facilities for Northern Ireland's three main sports - rugby, football and Gaelic.
Residents from about 60 nearby homes objected to the size of the planned development and launched a legal challenge to halt construction.
The GAA has repeatedly denied any wrongdoing and stressed it has an "impeccable safety record".
Representatives from the police and ambulance service also highlighted concerns about emergency evacuation arrangements.
Basil McCrea, NI21 MLA, said he found the safety experts' evidence had been "compelling".
He said: "I think you should have been listened to."