Two major donors to campaign group Cage have pulled funding in protest at the organisation's apparent defence of the Islamist militant Mohammed Emwazi, known as Jihadi John.
The Charity Commission revealed it had taken "robust action" to demand that the Joseph Rowntree Foundation and the Roddick Foundation would cease all current and future donations to the group.
Downing Street has labelled a claim MI5 may have contributed to the radicalisation of Mohammed Emwazi, known as "Jihadi John", as "reprehensible".
A Number 10 spokeswoman told a Westminster briefing: "It is completely reprehensible to suggest that anyone who carries out such brutal murders - they are the ones responsible and we should not be seeking to put blame on other people, particularly those who are working to keep British citizens safe.
"The people responsible for these murders are the people that we have seen in the videos."
Asked whether Mr Cameron shared the view of murdered British aid worker David Haines's daughter, Bethany, who said victims' families would feel closure only "once there's a bullet between his [Emwazi's] eyes", the spokeswoman replied: "The Prime Minister wants to see the murderers brought to justice."
Lawyers for Mohammed Emwazi's father have told ITV News there's no evidence his son is IS killer 'Jihadi John' as "his face is covered".
Newly released audio recording of Mohamed Emwazi, aka "Jihadi John", reveals his claims that he was threatened by MI5 five years ago.
"I really think that the focus of your outrage should be people who throw gay men off cliffs", said London Mayor, Boris Johnson.