Amal Clooney and her US-based colleague Jared Genser visited Mr Nasheed at the high-security Maafushi prison on Thursday.
Mr Genser told the BBC he believed the meeting was "bugged" after confidential details were leaked to the government.
Mr Nasheed was jailed for 13 years for ordering the arrest of a judge.
Mr Nasheed's wife received a phone call shortly after he met with his legal team on Thursday, from someone who had a key piece of information about the discussion, Mr Genser said.
"The only place it could have come from was that room," he added. "We therefore came to the conclusion that we had been bugged."
A spokesman for the Maldives Correctional Service denied that the conversation had been recorded, according to the Maldives Independent.
Mr Nasheed's legal team claim the case against him is political and that any surveillance is a breach of domestic and international law.
"I am disappointed but I'm not surprised. It is indicative of the government's approach to this case."
The former human rights campaigner became the nation's first democratically elected leader in 2008, ending three decades of rule by former strongman Maumoon Abdul Gayoom.
In 2012, he was detained after being accused of ordering the arrest of a judge.
He resigned months later amid an army mutiny and public protests over the judge's fate.
The UN said his rushed trial earlier this year was seriously flawed.
Mrs Clooney said on Thursday that she would push for sanctions against the Maldives unless it released her client.
"It is disappointing that it has come to this," she added.
International human rights lawyers defending the ousted Maldives president Mohamed Nasheed have accused the country's government of spying on them.