Moreland City Council

Ratnam first stood for and was elected to the City of Moreland (now City of Merri-bek) Council for South Ward in 2012.^[5] In 2016, she was re-elected with her vote more than doubling to 50.71%.^[8]

In 2015 she was elected by councillors as the first Greens mayor of Moreland for 2016 in a 6 to 5 vote with Independent Councillor Helen Davidson and Socialist Alliance Councillor Sue Bolton supporting her bid for the mayor.^[5] Her election as Mayor was even noted in the country of her heritage, Sri Lanka,^[9] and by the Indian community in Australia,^[10] and in Tamil culture.^[11]

In her time on the council, Ratnam was instrumental in removing official council references to Australia Day, saying “this is a gesture of respect and an important step in healing”.^[12] Ratnam resigned from the council on 11 October 2017.^[13]

2016 federal election

Ahead of the 2016 federal election the Greens preselected Ratnam to stand in the Division of Wills, where the sitting Labor MP Kelvin Thomson was retiring.^[14]

Although Ratnam substantially increased the Greens vote with a swing greater than 10 percentage points in Wills, the Labor candidate Peter Khalil won the seat with a 4.88 point margin.^[15][16]

State politics

Ratnam filled the vacant Legislative Council seat of former Victorian Greens leader Greg Barber, who announced his retirement from politics on 28 September 2017.^[17] On 12 October 2017, prior to having officially filled Barber's seat, Ratnam was appointed as leader of the Victorian Greens, becoming the first woman to lead the party at a state level.^[18][19] She was officially sworn in as a member of the Legislative Council on 19 October 2017.^[20]

Ratnam was re-elected in the Northern Metropolitan region at the 2018 state election, though her four party colleagues failed to win back their seats and she became the only Greens member of the Legislative Council.^[21]

Tenure

During her time in state politics, Ratnam has established parliamentary inquiries into the growing threat of far-right extremism (2022),^[22] the biodiversity extinction crisis (2019),^[23] and the waste and recycling crisis (2019).^[24]

According to The Age, between November 2018 and November 2021, Ratnam voted with the Andrews Government's position 62.4% of the time, the fourth-most of any Legislative Council crossbencher.^[25]

In 2023, Ratnam threatened to block a proposal by the Labor Party in Victoria to increase housing supply unless half of all new developments were either affordable housing or public housing.^[26] At the time, South Australia required that 15% of all new development were affordable housing, of which 5% were for the highest-need groups.^[26] She said that for the Greens to support reforms to increase housing supply, "the reforms must demonstrate that they meaningfully address housing affordability, and are not merely a free ride for the property industry."^[26] Ratnam also called for a two-year rent freeze.^[26]