Police are investigating Selangor Menteri Besar Azmin Ali under the Sedition Act 1948 over billboards put up across the state calling for former opposition leader Anwar Ibrahim to be freed from jail.

Azmin, who is also PKR deputy president, was summoned to the Petaling Jaya district police headquarters to have his statement recorded over the case.

The Gombak MP, who was accompanied by several PKR lawmakers, was questioned for more than an hour beginning at 4.10pm.

Azmin is being investigated under Section 4 of the Sedition Act 1948 for acts with seditious tendencies.

Speaking to reporters after having his statement recorded, Azmin described the investigation as a waste of time.

"This is a waste of public funds and time. I am disappointed at the police's rash action to investigate me based on unfounded accusations.

"They are using the Sedition Act to pressure me and the opposition leadership over something which even they are unclear what the offence is," he said.

Azmin said after his lawyers asked police to justify the investigation, it was revealed that the police were instructed to do so because the billboards had referred Anwar as a 'political prisoner'.

The United Nations Working Group on Arbitrary Detention also recognises Anwar as a political prisoner.

Azmin said the police would do better if they spend their resources on combating crime.

Inspector-general of police Khalid Abu Bakar had previously ordered for the "Free Anwar" billboards, which he described as seditious, to be taken down.

Anwar was in February last year jailed five years for sodomy, a charge he claimed was politically motivated.