Pakistan’s parliament has passed a controversial constitutional amendment that gives sweeping powers to the army chief and grants him lifelong legal immunity, a move critics have described as the “funeral of democracy.”

The 27th constitutional amendment was approved by the lower house on Wednesday with an overwhelming two-thirds majority, facing only four dissenting votes. The change further strengthens Field Marshal Asim Munir, Pakistan’s army chief, who is widely seen as the country’s de facto ruler.

The bill had already cleared the Senate on Monday after the opposition boycotted the debate. It will now return to the upper house for small changes before being sent to President Asif Ali Zardari for final approval, which is expected to be a formality. The quick passage of the bill has surprised many, as constitutional amendments in Pakistan usually take much longer to pass.

The new law creates the post of Chief of Defence Forces, putting the navy and air force under Munir’s command along with the army. Even after his term ends, Munir will retain his rank and enjoy lifelong legal immunity.

Prime Minister Shehbaz Sharif called the move a step toward unity and institutional balance.

“If we’ve made this part of the Constitution today, it’s not just about the field marshal,” Sharif said, adding that it also recognised the air force and navy. “What’s wrong with that?” he asked the speaker. “Nations honour their heroes … We know how to show and earn respect to our heroes.”

But critics say the changes give too much control to the military and the ruling coalition.

The amendment also shifts constitutional cases from the Supreme Court to a new Federal Constitutional Court whose judges will be chosen by the government. In the past, the Supreme Court has blocked several government decisions and even removed prime ministers, which some say explains the push for this new court.

Opposition lawmakers from Imran Khan’s Pakistan Tehreek-e-Insaf (PTI) party walked out before the vote and tore up copies of the bill, saying they were not consulted.

“None of the parliamentarians cared about democracy and the judiciary being eliminated. They have voted for being a silent observer whilst the country becomes a banana republic,” PTI spokesman Zulfikar Bukhari said. “Rest in peace Constitution of Pakistan.”

Legal experts have warned that the amendment could destroy the independence of the judiciary. “We are facing completely uncharted territory, a breach in our judicial system the likes of which we haven’t seen in almost a century,” said constitutional lawyer Asad Rahim Khan.

“The members slapping each other on the back should prepare themselves for when they’ll be seeking relief from the same courts they have destroyed and subordinated to the state.”

Another lawyer, Mirza Moiz Baig, said the amendment was “the death knell of an independent judiciary,” as it allows the prime minister and president to pick the chief justice and other judges of the new court, limiting its power to question the government.

The military has always played a major role in Pakistan’s politics, but this reform gives it stronger constitutional authority that will be hard to undo.

“With the amendment’s passage, parliament has done what previous dictators could only dream of,” Baig said.