Pakistan's powerful army chief secured expanded powers and lifelong legal immunity on Wednesday when lawmakers approved a constitutional amendment that gives him sweeping authority over all military branches and limits the independence of the country's highest court.

Opposition politicians, judges and independent experts condemned the move as a stark sign of democratic erosion in Pakistan and a slide into authoritarianism.

Syed Asim Munir, the army chief whom President Donald Trump called his "favourite field marshal", is set to become Pakistan's chief of defence forces by the end of the month, a new title positioning him over the navy and air force as well.

Under the new constitutional amendment, the field marshal and Pakistan's President, the country's symbolic head of state who also holds important powers over appointments and interim governments, will also be granted lifelong immunity from any legal prosecution.

"He's brought control of the military under himself," Ayesha Siddiqa, an expert on the Pakistani military, said about Field Marshal Munir.

Pakistan, a nuclear-armed country of 240 million people, has ebbed and flowed between civilian and military rule since its creation in 1947.

The last army chief to overtly run the country was Pervez Musharraf, who staged a coup in 1999 and was later named President until 2008. Since then, civilian governments have been nominally in control. But the military's grip on Pakistan's political and economic affairs has become so deeply entrenched that military and government officials have referred to the country's political system as a "hybrid rule" between the two.

The 27th Amendment to the Pakistani Constitution, passed on Wednesday, further tilts the balance towards the military.

"The civil-military hybrid system is a misalliance and destined to the same fate as most unequal marriages," said Shuja Nawaz, a veteran security analyst on Pakistani and South Asian affairs.

Besides the expanded powers enjoyed by Field Marshal Munir, a newly created court, whose judges will be nominated by the executive, will become the country's most powerful. It will operate above the current Supreme Court, which has at times acted as a check on army chiefs and governmental leaders but will now be reduced to handling civilian and criminal cases.

"Crony judges sitting in that new court will now rubber-stamp any judgment that the government would like to get passed," said Salahuddin Ahmed, a lawyer based in Karachi, Pakistan's largest city. Saad Rasool, another lawyer and public affairs commentator, said the reforms would cause "the collapse of an independent judiciary".

In letting Field Marshal Munir keep his title for life, as well as any equivalent for the navy and air force, the constitutional amendment widens the gap between the military's top leadership and lower ranks, said Nawaz.

New York Times News Service