Readers of The Argus are demanding Foreign Secretary Margaret Beckett take action to get Omar Deghayes home.
The Government has received a flood of postcards from Sussex campaigners fighting for Mr Deghayes, 37, from Saltdean, to be released from Guantanamo Bay, where he has been held for four years. He was arrested in Pakistan but has not been charged with any offence.
The Government's refusal to ask for his return was labelled "unlawful" in the Court of Appeal on Monday.
The Save Omar campaign group has produced a postcard to send to Ms Beckett, who is responsible for negotiations with the US.
The group said about 500 of the cards, depicting a prisoner kneeling on Brighton beach dressed in the Guantanamo prison's distinctive orange overalls, have been sent.
The Argus is sending the postcards on behalf of readers to let the Foreign Secretary know how the people of Sussex feel about the continued detention, without trial, of a British resident.
To join the campaign, download and fill in the coupon from here, put it in an envelope and post it to Newsdesk, Argus House, Crowhurst Road, Hollingbury, Brighton, BN1 8AR.
Louise Purbrick, of the campaign group, said: "We want to send as many as possible to Margaret Beckett to keep the pressure on her and the Government."
Mr Deghayes and his family, including brother Abubaker and sister Amani, came here in the Eighties from Libya after their father was killed by the Gadaffi regime.
His family are now British citizens. Mr Deghayes did not apply for citizenship and has been stripped of his right to remain in the UK because he has been "out of the country" for more than a year.
Abubaker Deghayes said: "The German Chancellor lobbied for the release of a Turkish national and German resident. All we are asking is that the British Government do the same for our residents."
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