But the 22 imams and scholars stopped short of condemning all suicide bombings, saying that those that target occupying forces in countries such as Israel and Iraq are sometimes justified.
"There should be a clear distinction between the suicide bombing of those who are trying to defend themselves from occupiers, which is something different from those who kill civilians, which is a big crime," said Sayed Mohammed Musawi, the head of the World Islamic League in London.
"The media in the West are mixing the difference between these two, and the result is that some of our Muslim youth are becoming more frustrated and they think that both are the same, even though Muslim law forbids killing any innocent lives," Musawi said.
Musawi spoke at a news conference at the London Central Mosque after the leaders and scholars read a statement condemning the 7 July attacks.
In their statement condemning the London bombings, the imams and scholars said the terrorism by a small group of radicals had victimised Muslims around the world by raising "Islamophobia" among the general public.
"We are firmly of the view that these killings had absolutely no sanction in Islam, nor is there any justification whatsoever in our noble religion for such evil actions. It is our understanding that those who carried out the bombings in London should in no sense be regarded as martyrs," the statement said.
It urged all Muslims and non-Muslims to help authorities investigate the crime and to punish those who helped plan the atrocity.
The statement also said that racism, unemployment and economic deprivation that Muslims face in poor sections of cities such as Leeds - where three of the suspected bombers lived - "may be alienating some of our children and driving them toward the path of anger and desperation" in ways that are prohibited by Islam.