An embattled former Tasmanian government mining minister who admitted to using an email address associated with a mining company he was supposed to have nothing to do with has claimed email filters protected him from being clued in on the company’s day-to-day activities.

Adam Brooks submitted his resignation to Tasmanian Liberal Premier Will Hodgman over the weekend due to a “perception of a conflict of interest” related to Brooks’ business interests and his ministerial responsibilities.

Brooks founded Maintenance Systems Solutions (MSS), a consultancy firm to mining companies, in 2004, and was elected to Tasmanian Parliament in 2010. He stepped down as the managing director of the company in 2012 while still in opposition but remained the sole shareholder of the company he founded until earlier this year. Brooks was promoted to the mining minister role in February this year and has been forced to slowly divest his interests in the company given his new ministerial role.

On Thursday, during budget estimates hearings, in an extraordinary exchange with Labor’s shadow treasurer Scott Bacon, Brooks first said three times that he was not using any company email, and then backtracked and said he still had an email account with the company but it was only for “personal use” and nothing to do with the business he had owned.

BROOKS: Chair, I wanted to clarify something Mr Bacon said. He alluded to some questions about relationships within MSS.  If I could ask him if he could cover off. I may have misheard the question; that is all.

BACON: It sounds like you misheard the question.

BROOKS: Could you repeat it for me?

BACON: I do not know what you are referring to.

BROOKS: I think it was related to phones or assets or emails or something.

O’CONNOR: Specifically, what it was related to clearly was an email.

BACON: Do not try this, mate.

BROOKS: No, I am not trying anything. I would like to clarify something with you, Chair. There is still a valid or an activated email owned by the company that I do not use for anything other than personal use. I obviously need to make sure that is clear. This is about a completely irrelevant attack on whether I receive emails.

This has raised questions on whether Brooks was still involved in the operation of the company given he was still actively using an email account administrated by the business while also being the minister responsible for the sector the business operates in.

Worse, Brooks claimed in his resignation letter to Hodgman, seen by Crikey, that although he did use the email address, he had set in place filters upon becoming a minister so that only personal emails would go through to his MSS email account.

“The MSS email address has been held by me for about a decade. Upon becoming a minister, a filter system was put in place to ensure any business-related emails were not accessible or able to be seen by me.”

Brooks said that since becoming a minister in March, he had only used it for personal and non-business-related correspondence, including his family and legal affairs.

Hodgman has asked the state’s Crown Solicitor to examine Brooks’ private MSS email server and all emails that were sent and received by the account to see if Brooks’ claims that a filter was set up on the account was strong enough to prevent all incoming emails except those related to his personal and non-business affairs. Hodgman told Parliament on Tuesday this investigation could take two weeks:

“It will also allow the Crown Solicitor to make an assessment independently and objectively – given his skills, qualification and position in government, he is well qualified to do so – as to whether any of the incoming or outgoing emails from the account indicate that Mr Brooks was participating in decisions concerning the operation of MSS or that he was provided information in relation to MSS that was not otherwise in the public domain.”

Brooks has not said what filtering exactly the company is using and whether there is an administrator to ensure that all appropriate emails were reaching him. The Labor opposition is likely to keep up the heat on Brooks and Hodgman while the Crown Solicitor attempts to determine what exactly Brooks had access to via the MSS email account.

Brooks’ case is similar to that of former member for Fairfax Clive Palmer, who was found to be continuing to use a Yahoo email address under the alias Terry Smith to sign off on expenses for Queensland Nickel. Crikey revealed that Palmer had also used this account to negotiate the passage of the carbon tax repeal legislation with Environment Minister Greg Hunt’s office. In his last press conference in Parliament, Palmer told Crikey that he used that email address for everything.

Prime Minister Malcolm Turnbull also uses his own private email server for government business.