Around half the estimated 700 Britons who have gone to fight with Islamic State jihadists in Syria have returned home, The Sunday Telegraph newspaper reported.
The weekly broadsheet's figures, in a story about a leaked draft of the Home Office interior ministry's new counter-extremism strategy, go further than previous estimates, of around 500 individuals leaving and 250 returning.
Around 320 "dangerous" jihadists have come back to Britain, the newspaper said.
The new counter-extremism plan involves targeting Muslim Sharia courts, a ban on radicals working unsupervised with children, and a requirement that job centres identify welfare claimants who may become radicalisation targets, the report said.
There would also be welfare penalties to encourage people to learn English, in order to improve integration, and tighter rules on granting citizenship to ensure newcomers embrace "British values", the broadsheet said.
The Home Office declined to comment on the report when contacted by AFP.
The Sunday Telegraph said it understood that the draft will be published before parliament is dissolved at the end of the month before the May 7 general election. (AFP)