The latest act of self-harm by asylum seekers in Darwin again demonstrates why alternatives to indefinite mandatory detention are urgently needed, the Australian Greens said today.

The Australian Greens will introduce new legislation on Monday to protect children from junk food advertising, after the Gillard Government and the Opposition wasted an opportunity earlier this year when they blocked Greens legislation despite public support for the Bill and recommendations from health experts.

"We have a burgeoning health crisis of childhood obesity and need to curb the relentless advertising of unhealthy foods to children," Australian Greens Leader Bob Brown said in Melbourne.

"The problem is not going away. It is getting worse. Self-regulation has clearly failed and the Australian parliament has a duty to act. This Bill is about the wellbeing of our community and future generations and expands on previous work by the Greens, to cover pay-TV and new media."

"Protecting children from junk food advertising is part of the comprehensive approach we need to take to manage the obesity epidemic in our community. Research clearly shows that the existing advertising industry code is inadequate, as the highest rating children's shows are being saturated with junk food promotions."

The Protecting Children from Junk Food Advertising (Broadcasting and Telecommunications Amendment) Bill 2011 would ban junk food ads on commercial television from 6-9am and 4-9 pm on weekdays from 6am-12pm and 4-9pm on weekends and school holidays, as well as banning junk food ads from pay-TV services aimed at children, in line Obesity Policy Coalition recommendations.

The Bill also places a prohibition on using the internet and digital services such as SMS and email to promote junk food to children.

The Obesity Policy Coalition includes the Cancer Council Victoria, Diabetes Australia - Victoria, VicHealth and the World Health Organisation Collaborating Centre on Obesity Prevention at Deakin University.

The Obesity Coalition's report into unhealthy food adverting is supported by the Australian Chronic Disease Prevention Alliance (including Cancer Council Australia, Diabetes Australia and the National Heart Foundation), the Australian Medical Association, and the Coalition on Food Advertising to Children.

The Prime Minister must not trade away vital health and social policies in her enthusiasm to cooperate with the US government in Trans Pacific Partnership free trade agreement talks underway in Hawaii, the Australian Greens said today.

"The United States, which is driving this agenda, is coming back to get what it didn't succeed in getting through the US-Australia free trade agreement," Australian Greens Deputy Leader, Senator Christine Milne, said.

"The Prime Minister must immediately release the negotiating text so that all Australians can see exactly what is under threat. The fact that the US is insisting it be kept secret is of great concern.

"The Greens support a fair trade agenda which enables greater global cooperation and trade and helps lift people out of poverty while improving workers' rights, environmental protection and social policies. A free trade agenda which waters down all these rights is not fair.