PKR has called on the Sarawak government to explain why Islam was stated as the official religion on the state government website, albeit briefly.

The website stated this as early as July this year, Sarawak PKR information chief Vernon Kedit said, but was amended to remove Islam as the official religion yesterday after the issue went viral.

Vernon said Sarawak PKR chief Baru Bian wrote to the state secretary on the matter five months ago but did not get an acknowledgement, so he raised the issue in the state legislative assembly last Wednesday.

"Today, we note that the offending entry on the website has been removed without any explanation.

"Therefore, we insist that either the chief minister or his state secretary issue an explanation as to why this gross error, regardless whether it was due to negligence, was allowed to happen and why no action was taken to rectify it when the state secretary's office acknowledged receipt of YB Baru Bian's letter of inquiry in July this year," he said in a statement.

"We expect nothing less than a firm and decisive declaration from the state government as this matter was the first non-negotiable point upon which the founding fathers of Sarawak agreed to form Malaysia in 1963," he said.

Islam is the religion of the federation, according to the Federal Constitution, but the Malaysia Agreement signed in 1963 states that Sarawak has no official religion.

Vernon added that the PBB-led government must also explain if this is proof that it is giving in to Umno's agenda.

Sarawak is the only state in Malaysia where Umno has no presence.

In the 2011 state election, PBB led by now state governor Abdul Taib Mahmud told voters that they should back the ruling state government or risk having Umno interfere in Sarawak affairs.

Billboards then showed a shark labelled Umno eating the other east Malaysian state, Sabah.

The Sabah government is led by Umno, which some east Malaysians regard as a "Malayan party" that puts the interest of Kuala Lumpur above that of the Borneo state.