In a speech, Ayatollah Khamenei made passing mention of the presidential system, which was his own route to power. “Presently, the country’s ruling political system is a presidential one in which the president is directly elected by the people, making this a good and effective method,” he said.

“However, if one day, probably in the distant future, it is deemed that the parliamentary system is more appropriate for the election of officials with executive power, there would be no problem in altering the current structure.”

There is little chance of such a change before the next presidential elections are due in 2013. But his comments will be viewed, including by Mr Ahmadinejad himself, as a further warning against overstepping the limits of the authority he is granted under Iran’s theocratic rule.