But Mr Alderton did respond when Mr Cosgrove asked if he could confirm that the commission had received in excess of 30 complaints from suppliers, telling him that was not the case.
He indicated that not all complaints received so far were about Countdown, but said that company's practices remained the focus of the inquiry at this point.
The commission has seven investigators working on the investigation which is expected to take several months.
Mr Alderton answered questions on the supermarket probe as commission chairman Mark Berry said he may have a conflict of interest on the matter. Dr Berry told the committee while in private practice as a lawyer few years before, he acted for suppliers over similar complaints.
The commission last month said it would formally investigate Mr Jone's complaint of anti-competitive behaviour by Countdown, and encouraged suppliers to come forward, promising anonymity for those who sought it.
Countdown has denied the allegations and says it will co-operate fully with investigation.