According to American media reports, declassified documents reveal that the US's National Security Agency (NSA) spied on the Pakistan Peoples Party (PPP) in 2010. The PPP was ruling the country then.
The documents revealed Monday show that the US spy agency was sanctioned to spy on most countries and some international bodies and political parties, including the PPP and the India's Bharatiya Janata Party, which now rules the country.
Under a 2010 certification approved by the Foreign Intelligence Surveillance Court, the NSA was permitted to spy on 193 foreign governments as well as foreign factions, political organisations and other entities, the Washington Post reported.
The PPP condemned the US for spying on the party and asked the government to raise the issue through diplomatic channels with the US.
"The revelation of spying on a major political party of Pakistan is a grave, unwarranted and totally unacceptable interference in the internal affairs of a sovereign country and is condemned," Senator Farhatullah Babar, spokesperson of the PPP, said in a statement.
Foreign ministry spokesperson Tasnim Aslam said Thursday that the issue was being raised with the US, Xinhua reported.
She said at her weekly press briefing that the US espionage in Pakistan is against international laws.