The head of the Charity Commission has warned that extremism is "the most potentially dangerous and deadly" problem faced by organisations after it emerged allegations of links between them and terrorist groups has almost trebled in three years.
The watchdog shared concerns about links between charities and extremism with police and other agencies 630 times in 2015/16, up from 234 in 2013/14.
Four inquires were opened into "allegations of abuse of charities for terrorist or extremist purposes" over the last year.
The 630 disclosures, which the Sunday Telegraph said was a record figure, related to "allegations made and concerns about abuse of charities for terrorist or extremist purposes, including concerns about charities operating in Syria and other higher risk areas, in which terrorist groups operate".
There were 21 reports of a "serious incident" and more than 70 visits or monitoring cases of charities which were identified as being at greater risk of terrorist or extremist abuse by virtue of their activities or where they operate, a report found.
William Shawcross, the commission's chairman, warned of the gravity of the threat currently faced by charities.
He told the Telegraph: "It is the most dangerous because of the threat of Islamist extremism. It is not the most constant threat – it is the most potentially deadly threat."
Mr Shawcross called for Muslim charities to help the regulator tackle threats of infiltration from extremists, saying it was within their interests to help avoid being caught up in a terrorist incident such as the murder of fusilier Lee Rigby in London in 2013.
He said: "A group of Muslim charity leaders came in to complain when I said this the first time and I said, 'Look, we are here to protect you if there were another atrocity on the streets of London, like the murder of Lee Rigby.
"'And, if an atrocity like the murder of Lee Rigby were in any way associated with your charity it would be catastrophic for you. We are trying to protect you and protect Muslim charities from that kind of abuse'."
The watchdog also wants to tackle fraud, financial abuse and protect vulnerable beneficiaries, stepping in during 2016 to stop the Joseph Rowntree Foundation and Anita Roddick Foundation funding controversial human rights group Cage, the newspaper said.
Cage - whose director is former Guantanamo Bay detainee Moazzam Begg - had attempted to encourage the "sabotage" of the Government's anti-extremism programme, Prevent, during meetings at universities.
Mr Shawcross also told the newspaper charities would, in future, have to pay for a new advice line so trustees can take action, following a series of scandals over data sharing and fund raising.