TEHRAN (Reuters) - Britain told Iran on Thursday it was happy to discuss its handling of street unrest after President Mahmoud Ahmadinejad accused its police of "savage" aggression against demonstrators. Britain helped lead Western condemnation of Iran's crackdown on protests against Ahmadinejad's re-election in June 2009. He was quick on Wednesday to criticize the British police's "crushing attack" on unarmed citizens. In a letter to Iran's Foreign Ministry, Britain's top diplomat in Tehran said she hoped such openness would encourage Tehran to allow a UN-appointed investigator looking into alleged human rights violations in Iran to enter the country. "I would remind you that the UK has a standing invitation to all UN special rapporteurs and has facilitated the visits of a number of these rapporteurs to the UK in recent years," British Charge d'Affaires Jane Marriott wrote, noting that Ahmadinejad had called for the United Nations to condemn Britain's action. "I urge the Iranian government to extend a similar courtesy to the dedicated UN special rapporteur for the Islamic Republic of Iran, Ahmed Shaheed, to enable him to address the international community's grave concerns about ongoing human rights violations within Iran."