Mr Somyurek quit the Labor Party last year before he was expelled following a Nine Network investigation, which allegedly caught him handing over cash and using parliamentary staff to create fake branch members.
Independent Broad-based Anti-corruption Commissioner Robert Redlich asked him whether he believed branch stacking was part of his public duty as a minister and an MP.
"I got initiated into this culture, and it was all sort of intertwined," Mr Somyurek said.
"It's not, strictly speaking, part of your brief as a minister and as a Member of Parliament, although the legislation isn't clear on that.
"It was so deeply embedded in the culture that it would be hard for people outside of the system to understand how embedded it is."
Earlier on Tuesday, the inquiry was played recordings of Mr Somyurek speaking to a factional ally about getting electorate staff to do factional work during office hours.
But he denied they were only given jobs to do that work.
"The purpose of these gentleman needing a job is that they got sacked for crossing over to our faction," he said.
"Then, I guess there are additional benefits, other things they want to do."
Mr Somyurek's evidence before the commission began on Monday, when he said Victorian Premier Daniel Andrews had dismissed his concerns about Labor's red shirts scandal before the 2014 election.
He claimed Mr Andrews replied: "Words to the effect of, 'Do you want to win the election or not?'"
Red shirts was a $388,000 scheme involving the misuse of parliamentary allowances to pay Labor's political campaign staff ahead of the 2014 election.
Mr Somyurek also described red shirts as "a gold standard rort" and criticised the Victorian Ombudsman for not coming down harder, saying she could have used "stronger language" to get the message across.
Asked about the claims, Mr Andrews said Labor had made "a number of important rule changes" since the Victorian Ombudsman's investigation into the scheme.
"We've taken unprecedented action. I have indicated to you and I will again that if we have to go further, we absolutely will," he told reporters on Tuesday.
He said Labor was "deeply regretful" of the red shirts affair and had already accepted responsibility for it and that he would appear before IBAC if asked to.
Mr Somyurek is appearing as a witness over four days this week, as the inquiry before Mr Redlich continues.
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