Minister Lizzie Blandthorn, who took over the planning portfolio this week as part of a cabinet reshuffle, is the sister of Hawker Britton director John-Paul Blandthorn.
Hawker Britton's clients include construction company John Holland, which is tasked with building the West Gate Tunnel, Mirvac, the Dennis Family Corporation and Melbourne Airport.
The planning minister has the power to make decisions around planning permits and land rezoning, but the state government says there will be arrangements in place to ensure any potential or perceived conflicts of interest are managed.
"All ministers are expected to act with integrity as they manage their portfolios to deliver the best outcomes for Victorians," a government spokesperson told AAP in a statement.
"The Secretary of the Department of Premier and Cabinet, the Secretary of the Department of Environment, Land, Water and Planning, and the Victorian Public Sector Commissioner are developing a robust management plan to ensure the independence of the Minister for Planning's decision making process."
Planning minister Lizzie Blandthorn referred to the government's written response when questioned by AAP.
Mr Blandthorn, who previously worked for premier Daniel Andrews and federal Labor MP Bill Shorten, has told the Victorian Public Sector Commissioner any contact he has with the planning minister will be done in the presence of an independent person.
In a letter sent on Monday, Mr Blandthorn said he would also seek meetings with the minister's staff rather than the minister herself, and he would keep a log of meetings with the minister's office.
"We believe it is in the best interest of Hawker Britton clients and seeks to uphold a higher standard of integrity between our firm and the Victorian Government," Mr Blandthorn said in the letter.
The Centre for Public Integrity is "very concerned" about the potential conflict of interest and wants to see an independent planning commission to determine planning approvals, similar to the NSW model.
"We're worried that in an area that's so sensitive and vulnerable to corruption, this personal relationship exists," executive director Han Aulby told AAP.
"On top of that, Victorian regulations around lobbying are some of the weakest in the country. The lobbying code of conduct isn't enshrined in legislation. There's no independent enforcement.
"The weaknesses in Victoria's lobbying regime make the risks even greater."
The planning minister's diary should also be made public so the community can scrutinise who they are meeting, Mr Aulby said.
Opposition leader Matthew Guy declined to comment on the planning minister, but said his party would improve Victoria's integrity system.
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