Iran enacted legislation on Monday to downgrade relations with Britain, in retaliation for intensified sanctions imposed by Western nations last week to punish the Iranians for their suspect nuclear development program. Britain promised to respond “robustly.”

The Guardian Council, an Iranian clerical body that has oversight on bills passed by Parliament, unanimously endorsed a bill approved on Sunday to expel Britain’s ambassador and reduce diplomatic contacts, Iranian news agencies reported.

The council determined that the legislation was “not in violation of Islamic principles or articles of the Iranian Constitution,” the Fars News Agency quoted a council spokesman as saying.

The United States and the European Union imposed harsher sanctions on Iran on Nov. 21 after the United Nations’ nuclear monitoring agency released a report on Nov. 8 that said Iran might be working on a nuclear weapon and missile delivery system.