Mir Hossein Mousavi, the runner up in the official results of the Iranian presidential election on 12 June is believed to be in the process of organising a general strike.
Mr Mousavi took part in demonstrations last week numbering hundreds of thousands of people in protest against the official election results which saw hardliner President Ahmadinejad elected with two thirds of the vote.
Mr Mousavi, his supporters and other defeated candidates claim the election was rigged and that Mr Mousavi is the true victor. Last week a leaked letter, which purports to be from the Iranian interior ministry but is impossible to verify, revealed that Mr Mousavi won the election and that Mr Ahmadinejad came third.
On his Facebook page Mr Mousavi posted a message saying, "We are working on a general strike plan. Please help us with your ideas if you have expertise on this issue."