People who received criminal convictions for having gay sex before homosexuality was decriminalised in Victoria are set to receive a formal state apology.

In a symbolic bid to rectify past injustices, the historic event will take place in the Victorian Parliament on May 24 – three decades after homosexuality was removed from the state's statute books.

Ombudsman Deborah Glass and her team will be marching and supporting the LGBTI community at Pride March. Credit:Joe Armao

Premier Daniel Andrews will make the announcement on Sunday as he attends the annual Pride March for the gay, lesbian, bisexual, transgender and intersex (GLBTI) community. Federal opposition leader Bill Shorten is also expected to take part in the event.

"Homosexuality was decriminalised in 1980, but for those convicted under the old laws, it's been a long wait to clear their names," Mr Andrews said.