The Home Office has been attacked for allowing Hizbollah-linked journalist Ibrahim Mousawi to enter Britain, days after Home Secretary Jacqui Smith announced plans to keep hate preachers out of the country.
Mr Mousawi edits the Al Intiqad journal in Lebanon and previously worked for the Shi'ite TV station, Al Manar.
He is believed to have received a visa from the British embassy in Beirut, where he is based, and travelled to London to take part in a course about Islam at the School of Oriental and African Studies (SOAS). One day of the programme was dedicated to discussions on Hamas and Hizbollah.
A CST spokesman said: "It is very disappointing that Mousawi was allowed into the country. It is even worse that he is here to lecture at a university."
Board of Deputies chief executive Jon Benjamin said: "We are extremely concerned that Mousawi has been given permission to enter the UK, without any particular conditions being attached. We have taken this matter up with the Home Office.
"Hizbollah uses its media operations to promote terrorism and vicious hatred of Jews. Mousawi is exactly the kind of figure who should be excluded from the UK under the new regulations."
The visit is believed to have caused divisions in Whitehall, with the Home Office, Foreign Office and immigration officials at odds over whether he should be allowed a visa. The Home Office refused to comment on Mr Mousawi's return. A spokesman said they could not discuss individual cases.
A SOAS spokeswoman said: "The programme has a wide range of speakers... Mr Mousawi was invited to participate in the programme as he is a leading expert on Hizbollah."
Mr Mousawi came to Britain last December for a Stop the War Coalition conference, and in February for a speaking tour arranged by the same group.