European Rugby Cup Limited is investigating alleged racist abuse during last week's Heineken Cup Pool Five match between Ulster and London Irish in Belfast.

The ERC disciplinary officer Roger O'Connor has written to the two clubs requesting full details of the alleged incident by January 3. He will then decide if there are grounds to proceed with a misconduct charge.

This week Ulster defended their second-row forward Matt McCullough after allegations by Irish that their full-back, Delon Armitage, was racially abused at Ravenhill. Irish, who did not name McCullough, confirmed that they had received a formal apology from an Ulster player for "foul and abusive language".

Ulster's chief executive, Michael Reid, said that was not an admission by McCullough that he had racially abused Armitage. "Ulster and Matt McCullough strenuously deny the allegation, made by London Irish, of racial abuse towards Delon Armitage," said Reid. "Matt has apologised by way of letter for the use of foul language towards Armitage in the heat of the moment during the match.

"This should in no way be misinterpreted as an admission to the use of racist language. We regard the allegation made by London Irish most seriously, as Ulster has an unblemished record in relation to racial issues."

PA