A cabinet minister has said the former Garda Commissioner should have acted sooner to inform the govenrment about illegal Garda taping.

Leo Varadkar says he's concerned that Martin Callinan knew about the taping last November, when the practice was ended - but waited until March before telling the Minister for Justice.

But other ministers have stopped short of sharing similar comments - though one Labour minister says he's confused as to why Minister Shatter didn't receive the commissioner's letter for a fortnight afterwards.

Our political correspondent Gavan Reilly reports.