An Indian Muslim preacher banned by the home secretary from entering the UK for his "unacceptable behaviour" is to challenge the ruling in the courts.
Zakir Naik, a 44-year-old television preacher, had been due to give lectures in Sheffield on 25 June and Wembley Arena the following day.
Theresa May said that visiting the UK was "a privilege, not a right".
The Islamic Research Foundation, based in Mumbai, India, said he was seeking a judicial review in the High Court.
The home secretary can stop people entering the UK if she believes there is a threat to national security, public order or the safety of citizens.
That includes banning people if she believes their views glorify terrorism, promote violence or encourage other serious crime.
However, somebody cannot be banned just for having opinions that other people would find offensive.
Ms May said: "Numerous comments made by Dr Naik are evidence to me of his unacceptable behaviour.
"Coming to the UK is a privilege, not a right and I am not willing to allow those who might not be conducive to the public good to enter the UK.
"Exclusion powers are very serious and no decision is taken lightly or as a method of stopping open debate on issues."
This is the first person who has been excluded from the UK since Ms May became home secretary last month.
Mr Naik is based in Mumbai, where he works for the Peace TV channel.
The Islamic Research Foundation said in a statement: "It is deeply regrettable the British Government has bowed to pressure from sectarian and Islamophobic pressure groups by preventing the entry of Dr Zakir Naik, who has been visiting and delivering talks in the United Kingdom for the past 15 years.
"Dr Zakir Naik is undoubtedly an opponent of terrorism and as such has often spoken out against all acts of violence and violent extremism.
"He has emphatically and unequivocally condemned the killing of civilians and is one of the world's regular noted orators on this topic.
"In the wake of the exclusion order and based on legal advice, Dr Zakir Naik intends to bring the matter before the High Court... and request a judicial review to have the exclusion order overturned."