Sutherland Shire MPs, who have previously advocated banning single use plastic bags, will be put on the spot when a vote is taken in State Parliament this month.
Attorney-General and Cronulla MP Mark Speakman and Heathcote MP Lee Evans publicly pushed for a ban in 2014.
Since then, major retailers Woolworths and Coles have stopped issuing single use plastic bags.
Opposition spokesman on the environment, Kate Washington said, "NSW is the only state in Australia that hasn't banned single use plastic bags reflects shamefully on this government.
"Thirty per cent of the world's turtles and ninety per cent of seabirds have now ingested plastic debris.
"Australians use more than four billion plastic bags every year - ten million or so each day - and we estimate 50 million of these plastic bags end up in our waterways and oceans."
Labor introduced the private member's bill, which was passed by the upper house but needs the support of the lower house to become law.
Mr Speakman told the Leader, "Plastics are a serious threat to our marine environment and ultimately to our food chain, with plastic rubbish expected to outweigh fish in the oceans by 2050 unless action is taken.
"As a government MP I will vote with the government as I was elected to do, but I will to continue to campaign actively and passionately within the government for strong action on single use plastics.
"This includes ending single use plastic bags, which I first spoke about in 2014."
Mr Speakman said while action on plastic bags was important, drink containers had accounted for close to half of litter and probably at least 40 times as much rubbish as plastic bags.
"That's why the container deposit scheme (legislated when I was Environment Minister, after 16 years of inaction by Labor governments) has been far more important," he said.
"There has been a 57 per cent reduction in eligible drink container litter in NSW since the CDS was introduced.
"We need a comprehensive strategy to deal not just with plastic bags, but with all single use plastics - including straws, cutlery, cups and packaging. I welcome the government's intention to develop one."
Mr Evans said, "There is no doubt that plastic bag waste and pollution is entering our natural environment, and we're doing something about it.
"With over two billion drink containers returned, this government is continuing successful initiatives to reduce plastics and litter in our community.
"The impact of single use plastic bags is significant, however we must also consider the consequences to small businesses.
"I will continue to advocate that the government continues its recycling and litter reduction initiatives."
Miranda MP Eleni Petinos said, "Single use plastic bags are a contributor to waste, but they are not the only contributor.
"By the end of the year, the NSW Government will release a discussion paper on a comprehensive plastics plan that will consider plastic waste holistically."
Maryanne Stuart, the Labor candidate for Heathcote at the 2019 election, said, "We want to reduce plastic pollution in our waterways and oceans, so we expect our local MPs to bring NSW into line with every other state and vote to ban single use plastic bags."