Mr Roberson said he did not want to comment on the legal action, "other than to say we are doing our job holding the Government to account''.
"There are serious questions to be answered here about the trust and confidence from the Government about how information about a private individual made its way into the public arena.''
"Untrue and defamatory statements have been made about me and my conduct in relation to the handling of information I received concerning an ACC claimant," Ms Collins said in a statement this morning.
"I value my reputation and take very seriously any accusations that I have acted improperly. This is not a course of action I take lightly.
"I have made myself extremely clear from the outset, that neither I, nor my office, has played any part in the release of the claimant's name to the media."
Ms Collins denied to Radio Live the move was a ploy to close down debate on the issue.
Privacy Commissioner Marie Shroff confirmed yesterday that she will investigate the email's trail from Ms Boag to an eventual report in the Herald on Sunday.
In the email, Ms Boag set out her account of a December meeting she attended between ACC claimant and former National Party insider Bronwyn Pullar and senior ACC managers.
All recipients of the email, including Ms Collins, ACC chief executive Ralph Stewart and ACC chairman John Judge have denied leaking the email to the Herald on Sunday.
The Herald on Sunday's report named Ms Pullar as the woman at the centre of a major privacy breach at ACC and identified Ms Boag as her support person at the December meeting.
At that meeting ACC claims Ms Pullar attempted to strike a deal to exchange the private information of thousands of other ACC claimants in return for a guaranteed benefit.
It subsequently emerged that Dr Smith, who was ACC Minister, wrote two letters supporting his old friend Ms Pullar's pursuit of her ACC claim, errors for which he resigned last week.
Ms Collins said the investigation, which she was told of early yesterday after a discussion with Ms Shroff on Tuesday night, was a "very good idea".
The commission's work "may involve computer forensic investigation", she said. "Frankly I welcome that."
Labour has been pressing for the Auditor-General to investigate Ms Pullar's use of her political connections to advance her ACC case and the role of ACC's board in setting up the December meeting.
In Parliament yesterday, Labour's Trevor Mallard questioned Ms Collins on her handling of Ms Boag's email, asking whether she or any of her staff discussed its contents with National party operative Lusk.
Ms Collins said she had not, but Labour's deputy leader, Grant Robertson, pressed the attack later in a general debate.
"We know there are many National Party figures involved in this."
Mr Robertson called on Ms Collins to ensure all emails in and out of her office, text messages and phone calls were made available to the Privacy Commissioner.
Mr Lusk was the manager of the Vote for Change campaign against MMP last year and among other roles has served as Napier MP Chris Tremain's campaign manager, in 2008.
WHO SAW EMAIL
* Michelle Boag - the sender of the email and Bronwyn Pullar's friend and supporter.
* ACC Minister Judith Collins - the recipient of the email who then forwarded it to:
* ACC chief executive Ralph Stewart and his secretary, and:
* ACC chairman John Judge.
