ISLAMABAD, Pakistaninfo-icon -- The lower house of Pakistan's Parliament overwhelmingly adopted a constitutional amendment on Thursday giving equal rights to millions of people in its restive northwestern tribal regions and ending a much-criticized legacy of British colonial law.

The measure also paves the way for the merger of the seven tribal regions, known as the Federally Administered Tribal Areas, with Khyber-Pakhtunkhwa Province, bringing the regions into the political and legal mainstream of the country.

The amendment goes to the upper house on Friday for final approval, but it is not expected to face opposition. The governing Pakistan Musliminfo-icon League-Nawaz and the major opposition parties Pakistan People's Party and Pakistan Tehreek-e-Insaf have supported the amendment, which was adopted by a vote of 229 to 1 in the lower house.

The federal government has administered the northwestern tribal regions, which are along the border with Afghanistaninfo-icon, since the country's independence from Britaininfo-icon in 1947. But it continued to use a harsh set of British colonial laws, known as the Frontier Crimes Regulations, that have been denounced by rights groups and political parties.

The colonial laws denied basic legal rights -- the right to a trial, for instance -- and used collective punishment against tribes or families for the offenses of an individual. The regulations, coupled with the lack of economic development, have led to a pervading sense of neglect and disenfranchisement among the tribal population. Over the years, the tribal regions have remained lawless, providing a haven for militants, gun runners and drug smugglers.

Without provincial status, the regions have also suffered from a lack of national investment. Much of the area, with an estimated population of five million, lacks clean drinking water and has limited healthinfo-icon care, education and telecommunication facilities. "Today, this house has approved a historic bill, which will have very positive effects for Pakistan," Prime Minister Shahid Khaqan Abbasi said on the floor of Parliament. "We need to provide people of the tribal regions with all those facilities that are available to the people in the rest of Pakistan."

Imran Khaninfo-icon, the leader of Pakistan Tehreek-e-Insaf, who is seen as the top challenger in general electionsinfo-icon expected by the end of July, called the amendment a triumph of the people. Mr. Khan has long advocated the merger of the tribal regions into Khyber-Pakhtunkhwa Province, where his political party holds power.

The country's powerful military also put its weight behind the merger, saying that it wanted to focus on the country's eastern and western borders and that a single system would help bring stability to the regions.

An influential civil-rights campaign that grew among the country's Pashtun population has sharply criticized the military's dominance in the tribal regions, where Pashtuns are the majority. Military actions have displaced a large part of the population, and officials have long been accused of involvement in extrajudicial killings and enforced disappearances.

Mohsin Dawar, a leader of the movement, known by the initials P.T.M., welcomed the extension of judicial protections to the tribal regions but stopped short of supporting the merger. "Our entire struggle is based on the right to live," Mr. Dawar said, adding that the movement would continue to protest against official abuses.

Some politicians and residents had asked that a separate province be created for the tribal regions, and expressed concerns about the financial viability of the merger.Still, people across the tribal regions by and large hailed Thursday's vote.

"This is a historic day for usinfo-icon. We have been demanding our basic human and legal rights. And, today our dream finally came true," said Malik Sangeen Khan Mehsud of South Waziristan.One analyst called the move "bold."

"With its capricious system of justice and lack of full political representation, the tribal areas had become an embarrassment to the country's elected leadership," said Joshua White, a fellow at the Brookings Institution. "But in moving to reform the tribal areas, they should be commended for taking a bold and long overdue step to remedy a historyinfo-icon of egregious disenfranchisement."