Greenpeace said the Federal Government should stop the approval process for the dredging of Abbot Point Coal terminal until more scientific research was conducted.
The Great Barrier Reef Marine Park Authority told a Senate hearing that yet-to-be released research shows ocean currents are moving dredge spoil further than indicated by industry modelling.
Greenpeace spokeswoman Louise Matthiesson says Federal Environment Minister Tony Burke should hold off on any decisions until the research is released, ABC reported.
Burke has until July 9 to make a decision on the dredging plan put forward by North Queensland Bulk Ports.
"It sounds very alarming the amount of mud stirred up by dredging is much greater than what we thought and the dredge plumes are spreading much further than we thought," Matthiesson said.
"Now [Burke] can push the pause button and request more information.
"He can basically allow more time for the scientific research to come into the public realm and for us to really understand what the latest science is telling us."
Matthiesson said the group was opposed to expanding coal ports in Queensland, and aim to draw attention to environmental issues.
"Our position, we are opposed to expanding coal export out of Abbot Point, and that includes opposing the dredging," she said.
In 2009, the Hay Point coal export terminal in Mackay was shut down for two days by Greenpeace protesters who chained themselves to the top of the coal terminal 50 metres above the ground for 36 hours in order to disrupt coal exports.
The protest is said to have cost the mining industry $20 million.