The advocacy group's findings represent the latest challenge to the plan. There are also serious doubts about how Pakistan could finance the at least $1.5 billion needed to construct the pipeline and whether it could go through with the project without facing U.S. sanctions in place over Iran's nuclear program.
"This gas will be an economic disaster for us," said the lead author of the report, Arshad Abbasi, at its release in Islamabad.
The chief guest was Shamsul Mulk, an ex-chairman of Pakistan's water and power authority and former head of the advocacy group's board of governors. Many other former senior officials and academics are affiliated with the institute.
The report called on the Pakistani government to renegotiate its contract with Iran and uncouple the price of gas with the cost of oil. That could produce lower gas prices that are closer to Pakistan's domestic cost of gas.
The agreement with Iran stipulates that Pakistan must construct its side of the pipeline by December 2014. If the country fails to meet this deadline, it will be liable to pay fines that could run into the millions of dollars per day.
The Iranian government says it has built 900 kilometers (560 miles) of the pipeline on its side of the border, with about 320 kilometers (200 miles) remaining to be built inside Iran. The Pakistan segment of the pipeline is expected to be about 780 kilometers (500 miles) and has not yet been constructed.
The U.S. has opposed the project, instead promoting an alternative pipeline that runs from the gas fields of Turkmenistan to Afghanistan, Pakistan and then to India. The U.S. also has championed a number of electricity generation projects within Pakistan, such as helping renovate hydropower dams.
The advocacy group also championed the use of hydropower, which is much cheaper than gas but can require significant up-front costs.
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Associated Press writer Munir Ahmed contributed to this report.