Toulouse lock Trevor Brennan has defended his actions during Sunday's match against Ulster, when he was involved in an altercation with a member of the crowd.

Brennan is likely to face a lengthy suspension and possible fine after wading into the crowd and punching a supporter during the Heineken Cup clash, but while he admitted regretting the incident today, he also stopped short of apologising for his actions.

"When I was warming up, I heard a group of supporters sing: 'Brennan, your mother is a whore'," said Brennan in a statement. "One of them looked me in the eyes, and again started to sing 'Brennan, your mother ...'. I then climbed the wall and had an altercation with this person. I regret this incident. But I didn't initiate it. That is the last thing I wished to do."

Brennan added he had a good relationship with Ulster fans but insisted such provocation was unlike anything he had experienced before. "I have always respected and I have always been respected by opposition supporters," he added. "I have often played against Ulster and not had these problems. I met their supporters days earlier and it was a true pleasure. I love rugby, I love Toulouse and the supporters, but I love my family and my mother more than all that."

Toulouse have launched a robust defence of their player, saying in their own statement: "Trevor Brennan is a generous man who has always respected opponents and their supporters. It required sustained and repeated provocation to make him react in an unacceptable but understandably human way. [Rugby is a] sport which has always placed an emphasis on the values of friendship and camaraderie. We want European Rugby Cup (ERC) to investigate the behaviour of some of the Ulster supporters."

BBC Northern Ireland journalist Julian Fowler, however, who was in the crowd during the match, insisted that the provoking chant had actually related to Brennan's pub. "Brennan climbed over a barrier and walked up the steps to the eighth row where a fan was sitting," he said. "A sustained attack followed and I saw at least six punches being thrown with both fists being used. The supporter was a young fellow and I would not say that he was in any way drunk or aggressive. He was left with a bloodied and swollen face: I saw him at the airport six hours later and he told me he was still in a state of shock, not knowing why he had been singled out."

Brennan, a 33-year-old Dubliner who won 13 caps for Ireland between 1998 and 2001, later appeared in the game, and was yellow-carded after exchanging blows with Ulster's Australian lock Justin Harrison. ERC announced their disciplinary officer Roger O'Connor will probe the off-field incident. O'Connor has contacted Toulouse and Ulster asking them to supply full details, and he has also requested reports from the match officials and broadcasters at the game. Following his investigation, O'Connor will decide whether to lodge any misconduct complaints.

Ulster were unhappy at the way events unfolded, releasing a statement on their return to Ireland. "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," it read. "During the match between Toulouse and Ulster in Toulouse on Sunday, 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."