Malaysia's opposition said Friday that their leader Anwar Ibrahim, who is under investigation on sodomy charges, will not give a DNA sample for fear it could be manipulated.

Anwar, a former deputy premier who has mounted a comeback after being sacked and jailed on sodomy and corruption charges in 1998, spent a night in police custody this week after being arrested on the new allegations.

He submitted to a medical examination but refused a request to give a DNA sample, drawing fire from the government, which said he should have nothing to hide.

"Under our laws, we cannot force a person to give a blood sample and if an application is made to court, given the current circumstances, we will resist it," Anwar's lawyer Sivarasah Rasiah told reporters.

"There has yet to be any credible justification for resorting to DNA analyses when the police report made by the complainant remains shrouded in secrecy and no evidence substantiating the allegations are available," he said.

Sivarasa also said since Anwar had provided alibi evidence to the police there was no need for the DNA.

"All the details of the alibi have been given to the police, but I am not at liberty to discuss it.

"It has all been given to the police so that is why we are also questioning why they are so focused on DNA evidence," he said.

Syed Husin Ali, deputy president of Anwar's Keadilan party, said police could not force Anwar to give a blood sample and ruled out the government's suggestion of involving foreign medical experts.

Anwar was freed Thursday on police bail and rushed home for medical treatment for an old back injury that he said had flared up during a night on a concrete floor in a bare cell at Kuala Lumpur police headquarters.

"There is no problem with him giving his sample. The problem is what happens to the sample after it has been given. It is completely in the hands of the Malaysian police," Syed Husin told AFP.

He said there was "no guarantee" a DNA sample would be used legitimately to investigate allegations by 23-year-old Mohamad Saiful Bukhari Azlan, a former aide to Anwar who accused him of sexual assault at a luxury condo last month.

"The police are capable of doing all kinds of things with the sample, especially since they have the person who is accusing Anwar in their custody," he said.

"We have reached a stage where we can't trust the police or the attorney-general's office."

Deputy police chief Ismail Omar said all legal avenues were being studied to see how they could obtain Anwar's DNA.

Anwar has rejected the allegations as a conspiracy designed to stop him from ousting the government, which was badly weakened in March elections that handed the opposition one-third of parliamentary seats.