Karadzic faces 11 charges alleging he masterminded Serb atrocities throughout the Bosnian conflict and faces a maximum life sentence if convicted.
He has boycotted the trial since it started in October, saying he was not ready to defend himslef despite first being indicted 13 years ago.
Harvey was appointed by the court last month to step in and act as a defence lawyer if Karadzic, who says he wants a lawyer from the Balkans appointed to defend him, continued to boycott the case.
Robinson said Karadzic wanted a lawyer "with a shared common heritage, language and trust" and with first hand knowledge of the 1992-1995 Bosnian war.
If the tribunal refuses, "Dr Karadzic can be certain that he will not receive a fair trial in this institution," Robinson wrote in Friday's motion.
Robinson said that funding issues with Karadzic's defence team mean that he "is not really prepared" to return to court on March 1 despite working 10 hours a day on his case from his detention unit cell.
Karadzic says he has to sift through 1.3 million pages of evidence as he prepares his defence.
"He's a night owl," Robinson said. "He likes to work in the middle of the night. He's working until four, five in the morning."
Karadzic faces two genocide counts for allegedly commanding Bosnian Serb forces who massacred about 8,000 Muslim men in the UN-protected Srebrenica enclave in July 1995 and for orchestrating a campaign of ethnic cleansing aimed at driving Muslims and Croats out of Bosnian towns and villages he claimed were part of a "Greater Serbia".
He was arrested in Belgrade last July after 13 years on the run.
Karadzic had been posing as a New Age healer named Dr Dragan Dabic, and had disguised himself with thick glasses, a bushy beard and straggly grey hair.
Presenting a report to the UN Security Council in New York on Thursday, Serge Brammertz, the UN's chief prosecutor, said Serbia has stepped up its co-operation with UN efforts to prosecute alleged war criminals, but needed to boost moves to arrest Ratko Mladic and Goran Hadzic who are still on the run.
|Brammetz said Serbia was co-operating in the search for alleged war criminals [AFP]
Brammertz said: "Serbia's co-operation with my office has continued to progress ... prosecution requests to access documents and archives are being dealt with more expeditiously and effectively."
Mladic, the former Bosnian Serb military leader, was indicted by the ICTY in 1995.
He is accused of being behind the 44-month siege of Sarajevo that left 10,000 people dead and the Srebrenica massacre.
Hadzic, the former Croatian Serb leader, is wanted for the murder of hundreds of people and the deportation of tens of thousands of Croat and non-Serb civilians during the 1991-1995 Croatian war.