More than 100 of Australia's brightest young citizens, led by astronomer and 1999 Young Australian of the Year Bryan Gaensler, have objected to the Prime Minister over what they say is the government's attempt to dehumanise refugees trying to escape persecution.

In a letter to John Howard, the group accuses the government of legitimising intolerance in Australia.

The letter, signed by 137 Australian graduates now working around the world, says: "We are deeply concerned that Australia's international standing as an open and tolerant nation has been compromised."

One of the signatories, Andrew Leigh, of Harvard University, delivered the letter to the Prime Minister's office on Tuesday. Copies have gone to Governor-General Peter Hollingworth and to other political leaders.

Other signatories include Hilary Charlesworth, of the Harvard Law School, Evan Kaldor, of Morgan Stanley's strategic planning group in New York, and John Romalis, of the University of Chicago's economics department.

Dr Gaensler, now at the Harvard- Smithsonian Centre for Astrophysics, said yesterday he spoke to friends after being depressed by what was happening.

"The friends spoke to friends and we had the signatures in four days," he said. "They represent a broad slice of the Australian community but include the cream of the crop of the expat community."

The letter strongly objects "to the government's use of language that dehumanises and vilifies refugees trying to escape persecution".

It goes on: "We feel that, as Prime Minister, you have a responsibility to encourage Australian citizens to overcome their fears and uncertainties about the significant changes that are currently taking place in the international sphere. Instead, we believe that your government has framed the debate in a way that gives legitimacy to intolerance in the general community. We ask you to move beyond populism and to conduct Australia's affairs in a way that reflects our status as a forward-thinking nation.

"We call on the Australian Government to comply with its international treaty obligations with respect to refugees and to meet its responsibilities as an international citizen in responding to humanitarian disasters.

"We call on the Australian Government to respond to the current refugee crisis (as it did for East Timor) by increasing the number of available places in the Humanitarian Program for the refugees currently fleeing Central Asia and the Middle East.

"We call on the Australian Government to put an end to mandatory detention and to inhumane treatment of asylum seekers."

Dr Gaensler said that if the post-war Australian government had acted like this one he would not be an Australian because his grandparents had fled the Holocaust.