Australian Nuclear Science and Technology Organisation chief executive Adrian Paterson was comforted by Senators and staff, and refused to leave the room until the man had left the building.

Listening to Mr Paterson give evidence was former ANSTO worker and whistleblower David Reid, who worked at the facility for almost 30 years, including years as his colleagues' occupational health and safety representative.''You're a liar,'' Mr Reid growled when Mr Paterson finished telling the inquiry he did not believe the incident had occurred.

''You've fabricated the findings, covered up safety incidents … you guys covered it over. You're a lying piece of shit.''

Mr Reid later told The Age he had been sacked after bringing claims of the incident to management. ''It's trashed my life; I've just been obsessed with it. My marriage fell apart, and I lost my house and I'm living in a caravan. But I can't let it go.''

The fracas centred on an incident that allegedly took place at ANSTO's Lucas Heights facility in 2007, which has been the subject of multiple inquiries, and remains disputed by all parties involved.

KPMG conducted the most recent investigation into the incident, reporting in June that many current and former ANSTO employees had ''imprecise at best'' recollections of the incident. But it found the regulator - the Australian Radiation Protection and Nuclear Safety Agency - failed to properly investigate the matter and neither its interim, nor final inspection reports, ''sufficiently examined allegations that a contamination incident … occurred''.

Greens Senator Scott Ludlam called for ANSTO to apologise to Mr Reid.

''I think what has to happen from here, Mr Reid is clearly owed an apology, but the regulator is going to have to step up.''