Iran has announced plans to build 10 new uranium enrichment plants and said work would start within two months.
Each site will be the size of the existing Natanz plant and aim at producing between 250-300 tonnes of uranium a year.
The decision was made during a Cabinet meeting headed by President Mahmoud Ahmadinejad on Sunday, Press TV reported.
It comes days after Western powers backed an International Atomic Energy Agency (IAEA) resolution censuring Iran and ordering it to halt construction of a uranium enrichment plant near Qom.
Before the announcement Gordon Brown warned that the western powers would seek harsher sanctions against Iran if it ignored the vote.
This can be veiwed as Iran’s answer to his threat.
The BBC has described it as “a massive act of defiance likely to bring forward direct confrontation”.
However it is seen it will ratchet up tension, particulalry with Israel, which has been calling for more stringent measures against the Islamic republic.
Although reportedly in possession of nuclear weapons itself, Israel has repeatedly hinted that it would take military action to prevent Iran becoming a nuclear power.
Sunday’s announcement is likely to alarm Israel and lead to calls for military action against Iran.