Johor's Sultan Ibrahim Iskandar has called on the government to reverse two-decade-old amendments to Malaysia's Constitution which removed the powers of the nine monarchs to veto laws, and curbed their legal immunity.

In his latest remarks to push for more royal discretion, the ruler said: "It is not proper to limit or abolish the power of the King or the Sultan in examining and giving their Royal Assent for laws".

"This just reduces the role of the King and the Sultans to mere rubber stamps for laws passed by the Parliament or the state legislative assemblies," he said when opening the 2016 Conference of Parliamentary and State Assembly Speakers of Malaysia in Johor Baru on Saturday.

Nine of Malaysia's 13 states are ruled by hereditary Malay Sultans, who take turns being the Agong, or King, of the federation for five-year terms. They act as constitutional monarchs while executive power rests with the Prime Minister and his Cabinet at the federal level. At the state level, the menteris besar and chief ministers make the executive decisions.

Without referring to Umno by name, Sultan Ibrahim in his speech said "a Malay political party had limited the powers of the King (Agong). What is worse is they forced the Agong to act according to whatever is the advice of the Cabinet".

The Johor ruler said the constitutional amendments made in 1994 "grabbed the powers of the King for the sake of political or individual interest". He added: "I hope this can be rectified."

The Umno-led ruling coalition curbed the powers of the royal houses following two major constitutional crisis in - 1983 and 1993.

The first one arose when the Mahathir Mohamad administration changed the Constitution to give Parliament and state assemblies the right to overrule any royal veto over legislation.

The powers of the royals were curbed further following two incidents of assaults in 1992 involving a Johor hockey goalkeeper and the coach, which allegedly involved top royal figures. The government amended the Constitution in 1993 to remove the immunity of the royal families.

Further changes meant that Bills passed by any legislature would become law after 30 days, regardless of whether the monarch concerned dissented.

The Johor sultan and his sons have been making waves over the past year by stressing their role in safeguarding the interest of their subjects, a period in which Prime Minister Najib Razak has been under siege over financial scandals.

It is not clear if what Sultan Ibrahim said is supported by the other eight houses. But the rulers have been flexing their muscles on several occasions in recent years, most notably in the appointment of menteris besar in Perak, Selangor, Perlis, Terengganu and in Johor itself.

The Najib government has not responded to the latest call by Sultan Ibrahim. But the call to amend the Constitution is unlikely to gain a foothold as no coalition now commands the necessary two-thirds of Parliament.

There has also been no popular movement to restore the royal privileges.