Macedonia's government has been accused of operating an illegal wire-tapping programme targeting 20,000 people, including opposition politicians.
Zoran Zaev, head of the opposition Social Democrats, said Prime Minister Nikola Gruevski had also spied on journalists and religious leaders.
Mr Gruevski has accused Mr Zaev of trying to blackmail him.
Macedonia is a candidate for EU and Nato membership. It went to the brink of civil war in 2001.
The violence was halted by a power-sharing agreement between the government and ethnic Albanian rebels. The deal saw many of the rebels enter a governing coalition.
The landlocked Balkan country is home to some two million people, about a quarter of whom are ethnic Albanians.
Addressing reporters on Monday, Mr Zaev said the government's surveillance programme had also targeted ethnic Albanian politicians.
He played brief recordings of what he said were excerpts from conversations that had been recorded illegally.
Mr Zaev said his party was seeking the prosecution of senior officials, including Saso Mijalkov, the interior ministry's intelligence chief.
The opposition leader has been saying for months that he would publish sensitive information implicating the Gruevski government.
The PM has in turn accused Mr Zaev of trying to blackmail him into holding an early election.
In late January, the police charged Mr Zaev with trying to topple the government with the aid of a foreign intelligence agency. Mr Zaev has denied the charges.