Bersih chairperson Maria Chin Abdullah's lawyer Ambiga Sreenevasan is urging police to allow access to her client before Tuesday's habeas corpus hearing.
Ambiga said Maria's lawyer and family members have not been allowed to see her since last Sunday.
"Please give us access to Maria for instructions on legal matters before her case on Tuesday.
"Have been trying to no avail," she said in a tweet to inspector-general of police Khalid Abu Bakar.
She added that an official request has also been sent.
Maria is held under the Security Offences (Special Measures) Act, which allows detention without trial for 28 days.
She was arrested on Nov 18, the eve of the mammoth Bersih 5 rally which attracted at least 40,000 people in Kuala Lumpur, to demand clean elections and clean government.
Her family said they have not received any information on Maria and do not know her whereabouts.
It is believed that she is held at the Batu police camp in Kuala Lumpur, where the now defunct Internal Security Act detainees were once held before they are moved to the Kamunting Detention Centre in Perak.
Human Rights Commission (Suhakam) visited her last week and said she was held in solitary confinement in a windowless cell, which only has a woooden bed with no mattress and access to cold water for washing.
Her family said the light is constantly on in her cell, disrupting her sleep.
Police said they nabbed her over documents found in the raid at the Bersih office, connected to American billionaire George Soros-linked Open Society Foundations.
Bersih refutes this, saying that there was no such document seized during the raid, according to the list of items seized provided by police.- Mkini