The ICTY decision represents the most drastic violation of Milosevic's fundamental human rights, Milosevic's Socialist Party of Serbia said in a statement on Thursday.
Denying Milosevic the right to defend himself is a crime and an attempt to strip him of his right to speak and say the truth about the break-up of the Yugoslav federation, the statement said.
Neither Milosevic, nor Serbia, nor the Serbian people broke up Yugoslavia, the party said and added that Yugoslavia was broken up by NATO member-countries which it said had founded the illegal tribunal in The Hague.
The party demanded that the bodies of Serbia and Montenegro take measures to protect Milosevic's human rights.
An association of Milosevic's sympathisers called "Sloboda" said the ICTY's decision represented an "unprecedented violation of human rights" showing that the tribunal's notion of a fair trial was the "medieval Catholic inquisition" and that ICTY regulations remained a dead letter.
The ICTY Trial Chamber on Thursday imposed defence counsel on Milosevic to avoid further delays in his war crimes trial because of his ill health.
Milosevic's defence attorneys are Britons Steven Kay and Gillian Higgins who have so far acted as "friends of the court" (amici curiae), in charge of the rights and interests of the accused who is defending himself.
An attorney from Belgrade, Branislav Tapuskovic, who had also acted as an amicus curiae, said the tribunal's decision was incomplete.
"The appointment of defence counsel does not solve the fundamental issue, and that is -- can the trial be held in case Milosevic is not in court due to his condition," Tapuskovic said.
Milosevic's legal advisor Zdenko Tomanovic said he did not expect friends of the court to assume the defence counsel role without additional preparations. He said one should wait for a decision by the trial chamber to determine the rights and jurisdiction of defence counsel.