Terry Hicks made the announcement in a statement through family spokesman Joan Shears at a Stop the War rally on Saturday in Brisbane, one of several demonstrations around the country marking the fourth anniversary of the invasion of Iraq.

Mr Hicks is believed to be accompanied on the trip by his wife Bev, who is David Hicks' stepmother.

"Our next visit will be going to Guantanamo Bay for David's appearance on March 27," said the statement, read to about 200 people.

"David's letters have been few and far between over the years and have been subject to censorship, and we have not received any correspondence from him since January 2005 due to his depression," it said.

"The last (telephone) call we were granted was in December 2006. However, David declined to speak to us and we were advised this was because he was emotionally distressed and did not think he could cope with talking to the family.

"We are very eager to speak to David and hear how he is and we are now even more concerned about his well-being."

• David Hicks Case Information