Brennan was warming up as a replacement on the sideline when he appeared to land several punches on the Ulster fan in the stands.

Brennan runs a popular bar in Toulouse and there have been reports that comments about the premise's quality were made from the crowd prior to the incident.

As if that weren't enough, after coming on as a replacement, the Irishman and Ulster lock Justin Harrison were later sin-binned for fighting.

But Ulster coach Mark McCall insists Brennan should have been given a straight red card.

"We will be lodging a complaint against Trevor Brennan for what he did to our player," said McCall.

"We are very lucky Justin has not got something seriously wrong with him."

Meanwhile, the Irish province plan to inform Heineken Cup organisers European Rugby Cup (ERC) of what they allege was an altercation involving Brennan and the fan.

The following statement has been released by Ulster Rugby against the former Ireland international: "Ulster Rugby has made the organisers of the Heineken Cup, the ERC, aware of an off-the-field incident involving the Toulouse player Trevor Brennan.

"During the match between Toulouse and Ulster in Toulouse on Sunday, 21st January, Brennan left the playing enclosure and physically assaulted a member of the Ulster travelling support.

"Ulster Rugby will be submitting a formal report to assist ERC in their investigation of this serious matter.

"Brennan was also involved in an incident on the field of play which Ulster Rugby will be reviewing."