As the same-sex marriage debate rages in Australia, the ABC is going back to where it all began. 

The national broadcaster has announced it has started filming a telemovie that explores the gay rights movement in 1970s Australia. 

Riot will explore the lives of real Australians who fought discrimination – and, at times, the law – in the name of equality.

The script is centred around civil rights activist Lance Gowland (1935-2008) and the events that lead to Sydney's first ever Mardi Gras. 

Gowland will be played by Australian actor Damon Herriman, who has starred in Offspring, Wilfred and more recently the second season of Top of the Lake. His fellow cast members include Xavier Samuel, Kate Box and Jessica de Gouw. 

The ABC's head of scripted production, Sally Riley, said the telemovie is bound to strike a chord with Australian audiences given the government's plan to hold a $122 million postal vote on same-sex marriage.

"It could never be more relevant than now to tell this story of identity, courage and love as a marginalised community finds its voice and rises up to fight oppression and injustice," she said. "With a cast as extraordinary as this, Riot promises to be a stirring, landmark television event in time for the 40th anniversary of the birth of Mardi Gras." 

The telemovie is being filmed in Sydney over the next four weeks and will make its debut on the ABC in 2018.