Gholam Reza Kateb, an MP on the national planning and budget committee, said the country's economy as a whole was in trouble.
Kateb said the steep export drop was revealed in a parliament report by Oil Minister Rostam Qasemi, the BBC reports.
According to the state-run media, he said that on the basis of the report, oil sales are down 40 percent and income has dropped 45 percent in the last nine months. 
International sanctions on Iran include a UN embargo on arms exports and nuclear technology as well as EU bans on most financial transactions as well as the purchase of crude oil.
The United States prohibits almost all trade with Iran.