An Islamist extremist who told audiences at Mosques and universities that Isis “were no different to western armies” and non-Muslims would be “punished in hell” was unwittingly employed at Her Majesty’s Inspectorate of Constabulary (HMIC).

For almost two years Abdullah al-Andalusi used the name Mouloud Farid to work at the heart of the British security establishment after he passed security vetting at the official regulator of all 44 forces in England, Wales and Northern Ireland.

It was only when his bosses saw him defending extreme Islamist views on television that his cover was unmasked, according to The Sunday Telegraph.

Part of the inspectorate’s work involves scrutinising police forces’ counter-terrorism capabilities and top-secret plans for dealing with terror attacks.

Reports on the use of informants and undercover policing have also been recently published by HMIC.

Mr Andalusi, whose real name is Mouloud Farid was a well-known figure on the extremist lecture circuit and closely associated with the extremist group Hizb ut-Tahrir, which believes that voting and democracy are un-Islamic, the Telegraph reported.

He is also a firm believer that British citizens should be allowed to fight in Syria and he spoke outside his own employer’s parent department, the Home Office, to demonstrate against the arrest of Moazzam Begg, the former Guantánamo detainee, on Syria-related terror charges that were later dropped.

“Mr Farid was investigated for gross misconduct by taking part in public activity that compromised his impartial service to government, thereby breaching the civil service code,” a spokesman for HMIC told the paper. “He was suspended immediately whilst investigations were ongoing.”