A state funeral will be held for Mr Twentyman at St Patrick's Cathedral on Tuesday morning after his death in late March at age 76.

The service will be open to the public and streamed online.

Mr Twentyman was best known for his advocacy for disadvantaged and vulnerable Victorians, tackling issues such as youth homelessness, drug abuse, prison reform and social welfare.

A foundation bearing his name, worked to engage young people with their education, families and communities.

Mr Twentyman's family has requested people contribute to the Les Twentyman Foundation in lieu of flowers.

Born the eldest of five children to fruit shop owners in 1948, he was raised in Melbourne's western suburb of Braybrook.

He was a member of the Save the Dogs committee when the Western Bulldogs AFL team, then known as Footscray, were close to merging with Fitzroy in 1989.

Mr Twentyman was a candidate for Victorian parliament's upper house in 1992 and 1996 and in the lower house at the Kororoit by-election in 2008.

He received an Order of Australia medal in 1994 for his service to youth as an outreach worker and was named Victorian of the Year in 2006.

Australian flags will be flown at half-mast on Tuesday across all Victorian government buildings as a mark of respect.

Australian Associated Press