The union representing STC staff, the Media Entertainment & Arts Alliance, also claims theatre management is putting commercial interests ahead of the health and safety of its staff.

The escalating dispute between the union and theatre company over the physical attacks is listed for hearing at the Fair Work Commission on February 4.

In the first incident, the MEAA says a female usher was forcibly pushed by a patron attending a performance of King Lear, starring Geoffrey Rush, at the Roslyn Packer Theatre in December.

The usher had been moving along an aisle past seated theatregoers when her walkie-talkie brushed the head of the audience member who then pushed her.

A complaint was made to police but later withdrawn, the union alleges, under pressure from STC management.

The second incident occurred just before an STC performance in January when a staff member was "forcefully" slapped on the back a number of times by a patron who then made an offensive gesture by grabbing his genitals.

"In both occurrences, staff had followed the STC procedures, and had done nothing to provoke the incidents," said Mal Tulloch, the director of MEAA's entertainment, crew and sport section.

The union alleges that the perpetrator of the first assault was a season ticket holder and a well-known patron to the STC, which accepted an apology and allowed the person to continue to attend shows.

The MEAA said theatre management did not adequately investigate the incident as required under health and safety laws.

"It was inappropriate and unreasonable that during this "investigation" they granted the patron in question the privilege to attend another production before the investigation was completed," it said in a written statement.

A meeting of staff on January 29 passed a resolution calling on the theatre company to develop "better procedures for reporting incidents [and] dealing with violent and intoxicated patrons".

Mr Tulloch said the STC had inadequate procedures for dealing with violent patrons.

"Furthermore, the victims of this violence felt isolated, frightened and felt lack of support by their employer," he said.

He reiterated the union's demand that the patron be barred from the theatre venue indefinitely.

"We are appalled and alarmed that STC is willing to put a paying patron's bad behaviour above the safety of its staff," he said.

STC spokesman Tim McKeough said the theatre company did not agree the first incident involving the season ticket holder was an assault based on advice from the police and its lawyers. He said the second incident was being investigated.