Iran's senior dissident cleric, Grand Ayatollah Hossein-Ali Montazeri, has attacked President Mahmoud Ahmadinejad over nuclear issues and the economy.
The grand ayatollah said Iran's tone could provoke enemies
The bold remarks came in a written statement by the 85-year-old, who was once in line to succeed Ruhollah Khomeini as supreme leader.
He spent years under house arrest after falling out with Ayatollah Khomeini.
He said nuclear energy was Iran's right, but questioned the way President Ahmadinejad had pursued it.
Using harsh and provocative language would provoke the enemy, Grand Ayatollah Montazeri said, calling instead for negotiations.
His comments came as a report by Iran's Isna news agency suggested that 38 inspectors working for the United Nations nuclear agency had been barred from entering Iran.
In a separate development, the European Union criticised Iran for not co-operating with the UN over demands that it curbs its nuclear programme.
Iran's Revolutionary Guards also announced several days of exercises in the centre of the country.
Two new types of Iranian-produced missile would be tested, one said to have a range of 75km (47 miles), the other 350km, state radio said.
The grand ayatollah spoke out against Mr Ahmadinejad in remarks to reformists and opponents of the president in the religious city of Qom last Friday, the Associated Press news agency reported.
Mr Ahmadinejad's handling of natural resources was attacked
Grand Ayatollah Montazeri compared Iran's natural resources favourably to those of other countries.
"Some countries don't have oil and gas. Yet, they run their country and stand on their own," he said, according to a copy of his words seen by AP.
"We have so much oil and gas but make useless expenditures work for others and don't think of our own people's problems and the price of basic commodities goes higher and higher every day."
He complained that people kept on shouting slogans about nuclear rights, but he asked: "Don't we have other rights too?"
It was a pointed reference to concerns about diminishing freedom of speech in Iran under Mr Ahmadinejad, says the BBC's Frances Harrison in Tehran.
Grand Ayatollah Montazeri also launched a scathing attack on the president's handling of the economy.
He said some claimed inflation was only 13% in Iran, but everyone knew the cost of housing had risen more than 50%.
He asked why the government went on what he called useless trips and spent money on others abroad, seemingly a reference to President Ahmadinejad's recent tour of Latin America and Iranian aid to Palestinian groups like Hamas.