More details have emerged concerning the exclusion order against Islamic speaker Raed Salah, who is currently being detained after allegedly flouting a ban to enter the country.

Sheikh Salah, leader of the northern branch of the Islamic Movement in Israel, was arrested last month, a day before he was due to share a platform with MPs in the House of Commons.

MP Mike Freer asked Home Secretary Theresa May about the case in the Commons on Monday, accusing Sheikh Salah of having a "history of virulent antisemitism".

Mrs May told the Home Affairs Committee today that she had signed the banning order on June 23, two days before Sheikh Salah entered the country . She only confirmed on June 27 that he had entered the country.

According to the Daily Telegraph, Sheikh Salah was able to enter Britain without being stopped because border officials believed he was flying to Terminal One rather than Terminal Five and sent an alert to the wrong place.

But Mrs May said there should not be speculation on what had happened and that a full investigation was taking place.

"There is a normal process that is undertaken by the UK Border Agency in relation to any exclusion orders that I sign," she said. "That process may differ depending on the circumstances of the individual who is being excluded from the United Kingdom. There is a normal process of notification and then obviously of indications to those at ports of entry that this is an individual who should not be allowed to enter the United Kingdom.

"That did not work in this instance. Something went wrong. We are urgently reviewing this to see what it was that went wrong."

She would not be drawn on the reason for the banning but said it was for "unacceptable behaviour".