The controversial Muslim cleric Yusuf al-Qaradawi has been refused a visa to visit Britain.
Yusuf Al-Qaradawi defended suicide attacks in Israel as "martyrdom"
The Home Office said the UK would not tolerate the presence of those who seek to justify acts of terrorist violence.
During his last visit in 2004, Dr Al-Qaradawi defended suicide attacks on Israelis as "martyrdom in the name of God", during a BBC interview.
Dr Al-Qaradawi applied for the visa eight months ago, so that he could receive medical treatment in Britain.
Reacting to the decision, the Muslim Council of Britain (MCB) called it deplorable, and said the government had caved in to unreasonable demands spearheaded by the leader of the Conservative Party, David Cameron.
Inayat Bunglawala of the MCB said the decision had "worrying implications for freedom of speech".
"Whatever one may think of some of Qaradawi's views, the way forward is surely to allow them to be aired and then, if appropriate, to challenge them openly."
'Dangerous and divisive'
Last week Mr Cameron called Dr Al-Qaradawi "dangerous and divisive", and called on the government not to allow him an entry visa.
"This decision will send the wrong message to Muslims everywhere about the state of British society and culture", said Muhammad Abdul Bari, secretary-general of the Muslim Council.
He said Dr Al-Qaradawi was respected as a scholar throughout the Islamic world.
Dr Al-Qaradawi, who was born in Egypt but now lives in Qatar, is already banned from entering the US.
Friends said he recently visited France and received medical treatment there.
Explaining the reasons for the visa refusal, a Home Office spokeswoman said: "The UK will not tolerate the presence of those who seek to justify any acts of terrorist violence or express views that could foster inter-community violence."
Mohammed Shafiq, from Muslim youth organisation the Ramadhan Foundation, criticised the decision.
He said: "We've had figures like Nick Griffin and the BNP operating freely and promoting violence towards ethnic minorities, and nothing is done.
"This smacks of double standards, and will isolate Muslim communities further."
The campaigning group, the British Muslim Initiative described the ban as "disgusting and outrageous" and said it was "an unwarranted insult to British Muslims and all Muslims around the world".
However, shadow home secretary David Davis welcomed the move.
"Not before time the government has finally acted after pressure from David Cameron," he said.
"The government's approach to preachers of hate has been at best timid and at worst downright useless.
"Now it is time for them to take a robust approach across the board."