The Victorian state politician brother of a convicted former federal Labor MP has stood aside waiting for the outcome of a police investigation.
Senior Victorian government minister Theo Theophanous has stood aside from cabinet pending a police investigation, he said.
Mr Theophanous, the member for the Victorian upper house Northern Metropolitan province, is the state's Minister for Industry and Trade, Major Projects and Information and Communications Technology.
He would not confirm the nature of the investigation but government sources say his decision was related to an alleged assault.
Mr Theophanous told a packed press conference he contacted Victoria Police on Monday following rumours over the past week police were investigating a complaint lodged against him.
"They have confirmed that this was the case. While I have not been advised by the police as to the nature of that complaint, I have been advised that the police are conducting interviews in relation to the matter," he said.
"I have been further advised that Victoria Police may wish to interview me in the near future in relation to their inquiries.
"I feel strongly that if a minister is the subject of a formal complaint which is being investigated by the police, he or she should stand down until the matter is cleared and cleared up by the police."
Mr Theophanous said he had done nothing wrong but was stepping aside temporarily in the interests of "complete propriety".
"I know that my decision to stand down will come as a shock to my extended family, my friends and the community that supports me," he said.
"I know that they will be concerned about me and my family and I want to assure them that I have no case to answer."
Police were equally tight-lipped about the case.
"It is not appropriate for Victoria Police to identify individuals who are involved in an investigation until such time as they are formally charged," Victoria Police spokeswoman Senior Constable Melissa Seach told AAP.
In a statement, Victorian Premier John Brumby said he accepted Mr Theophanous's course of action but would not comment further.
Treasurer John Lenders will act as Minister for Industry and Trade, Roads and Ports Minister Tim Pallas will cover the major projects portfolio and Environment Minister Gavin Jennings will look after information technology, Mr Brumby said.
The Cyprus-born father of four entered parliament in 1988 after tutoring in politics and social statistics at Melbourne's LaTrobe University.
His first cabinet post was as consumer affairs minister and minister for manufacturing and industry development under Joan Kirner's leadership in 1991.
He was also small business minister for nine months before the Kirner government was swept from office in 1992.
He was opposition leader in the upper house and spokesman for industry, employment and WorkCover for much of the 1990s.
In 1999, then leader John Brumby dumped him as the party's upper house leader for perceived disloyalty.
He returned to the front bench in 2002, first as resources and energy minister, then from 2006 to 2007 as minister for small business and state development.
He is the brother of disgraced former federal Labor MP Andrew Theophanous, who was convicted in 2002 of charges related to abuse of his powers by helping and advising in immigration matters in exchange for cash.
Andrew Theophanous was jailed for a minimum of three and a half years.