The federal opposition has been calling for Slater & Gordon to release full internal documents relating to the alleged misuse of AWU funds by Ms Gillard's then boyfriend and union official Bruce Wilson.
It says Ms Gillard, who was a partner at Slater & Gordon at the time, may have further questions to answer in relation to the matter.
Ms Gillard established the AWU's Workplace Reform Association in 1992 while she was working for Slater & Gordon.
She resigned from the firm following an internal review of the AWU matter.
Mr Grech said he was "not an actor" in the matters that occurred 20 years ago.
Mr Grech rejected the suggestion that the matter was affecting Slater & Gordon's reputation.
"Our reputation is well and truly intact, and I'm not aware of any serious journalist or any serious public commentator who has cast any aspersion on the conduct of anyone who is present at Slater & Gordon," he said.
Slater & Gordon has said that it is not able to release any files or documents in its possession without client approval, because to do so would breach its professional obligations.
The company has rejected any suggestion that it has withheld or delayed the release of files in its possession to any former clients.
AAP tsc/gfr/was
-AAP