Full video report by ITV News Deputy Political Editor Chris Ship
Defence Secretary Michael Fallon, who authorised the RAF killing of two British men in Syria, has suggested there were more names on the list who were legitimate targets for air strikes.
ITV News understands Mohammed Emwazi - the man known as Jihadi John, who has been filmed beheading hostages, is among at least five others on the list.
It comes after Mr Fallon, who authorised the killing of IS fighters Reeyad Khan and Ruhul Amin, said further drone strikes could be launched within weeks against IS militants plotting to attack the UK.
Speaking to ITV News, Mr Fallon said: "There are a number of terrorists involved, not simply those who were involved in the strikes a couple of weeks ago, and they've have been a series of potential plots that our agencies work extremely hard to try and disrupt."
Earlier he said the Government would "not hesitate" to repeat the action that led to Khan and Amin being killed by an RAF drone in the Islamic State stronghold of Raqqah last month.