Labor has called on Employment Minister Michaelia Cash to "come clean" about whether she is under investigation by the Australian Federal Police over media leaks relating to last year's AWU raids, after the AFP confirmed they believe criminal behaviour may have taken place.

"We do believe an offence may have been committed," AFP deputy commissioner Leanne Close told a Senate estimates hearing on Friday.

Ms Close declined to rule out whether Senator Cash, or Human Services Minister Michael Keenan, were interviewed in relation to the matter.

Employment Minister Michaelia Cash is under pressure over the AWU raid leaks. Credit:Fairfax

"It’s not in the public interest for the AFP to answer the question on the grounds that it may prejudice the ongoing investigation of a possible breach of law," the deputy commissioner said under questioning by Labor senator Murray Watt.