Thousands of people have protested Indian mining giant Adani's plans to dig a new thermal coal mine in Queensland and have called on state and federal governments as well as the federal opposition to stop it going ahead.

Protesters marched the streets in Melbourne, Sydney, Brisbane and Cairns just a week after upwards of 15,000 school students demonstrated against government inaction on climate change.

It follows the announcement last month by Adani it would self-fund the controversial project after scaling back its size and scope.

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The coal project is being downsized from a 60-million-tonnes a year, $16.5 billion mega-mine to a more manageable 10-to-15 million tonnes a year costing around $2 billion.

"No longer will we sit back and be lectured to by people who are outdated and out of touch," Thomas Cullen told hundreds of protesters gathered in Brisbane on Saturday.

The 17-year-old was one of the thousands of students criticised by Prime Minister Scott Morrison for skipping school to stage national strikes calling for immediate action on climate change just over a week ago.

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He travelled to Canberra this week for a sit in on the marble floors of parliament to confront Mr Morrison over the issue.

"We are preparing to show our leaders that we will not stand for their inaction," Mr Cullen said.

April McCabe, 24, says there is a growing sense of urgency among university and high school students who want their governments to do more to tackle climate change.

The Queensland public health and global studies student said news that major works on Adani's Carmichael mine in the state's Galilee Basin are imminent has provoked more young people to push for change.

"It has been talked about but now people are taking action," she said.

In Sydney, protesters carried an array of signs, including some reading "Time for a COALonoscopy", "There is no Planet B", "I bet the dinosaurs thought they had time too" and "The climate is changing, why aren't we?".

Jean Hinchliffe, 14, said Australia's political leaders were displaying continued ignorance and had tried to disregard the student climate change protest she headed in Martin Place last