"Apologists" for those who commit acts of terrorism are partly responsible for the violence, Philip Hammond has said.
Security services have been criticised over their handling of Mohammed Emwazi - known as "Jihadi John".
But in a speech the foreign secretary praised the "brilliance" of Britain's intelligence officers.
Mr Hammond also warned of Russia's "aggressive behaviour", saying it could "pose the single greatest threat" to the UK's security.
Gathering intelligence on Russia's intentions would be a "vital part" of the work of Britain's intelligence agencies for the "foreseeable future", he added.MI5 'harassment'
In another development due later, MPs are expected to approve new travel restrictions for people the government believes pose a "terrorism-related threat".
The motion will also introduce fines for airlines which breach a series of requirements set up to "prevent certain individuals from travelling to or from the UK".
In the speech at the Royal United Services Institute (Rusi) in London, Mr Hammond said ministers must act "decisively" in debates about powers given to the security services so they can "get on" with keeping the UK safe.
He said: "The exposure of the alleged identity of one of the most murderous Isil (Islamic State or IS) terrorists over the last few weeks has seen some seeking to excuse the terrorists and point the finger of blame at the agencies themselves.
"We are absolutely clear; the responsibility for acts of terror rests with those who commit them.
"But a huge burden of responsibility also lies with those who act as apologists for them."
Cage, an advocacy group for those "impacted by the War on Terror", has said MI5 played a role in the radicalisation of the Kuwait-born Briton.
Its research director Asim Qureshi told the BBC "harassment" by intelligence officers did not make Emwazi into a killer, but he said it was a factor in making him feel he "didn't belong in the UK anymore".