The report, prepared by the Committee for the Protection of Votes which is run by Mousavi's campaign office, accused President Mahmoud Ahmadinejad of abusing the state machinery during the campaign.
It charged that the hardline incumbent had distributed cash to secure the votes of working class Iranians.
The report accused the Interior Ministry, which was charged with organizing the election, and the Guardians Council - the official electoral watchdog - of being biased towards Ahmadinejad.
It said members of the council had publicly supported the incumbent before and during the campaign.
The report, posted on Mousavi's campaign website Ghalamnews late on Saturday, charged that some commanders of the elite Revolutionary Guards Corps had openly backed Ahmadinejad's candidacy and, along with the Basij militia, intervened in the voting process.
It asked why the Interior Ministry had printed 14 million more ballots than the total registered electorate of some 46 million.