London, England - Islamic extremists who incite violence or praise suicide attacks in Britain could face charges of treason.
The Crown Prosecution Service's anti-terrorism head is due to meet Scotland Yard officers in the next few days to examine whether treason charges can be brought.
The Government is focusing on three Islamic radicals living in Britain: Omar Bakri Mohammed, Abu Izzadeen and Abu Uzair.
Bakri has been of particular concern after urging Muslims not to give information to the police and apparently calling the July 7 suicide bombers "the fantastic four".
The move is an attempt to clamp down on extremists even before new legislation is drawn up.
The charges the Crown Prosecution Service will consider include the offences of treason, incitement to treason, solicitation of murder and incitement to withhold information known to be of use to police. These offences include attacks made against British interests abroad as well as at home.
However, Lord Carlile. the Liberal Democrat peer appointed as the independent reviewer of anti-terror legislation, said he would be "very surprised if treason was used".
"It is remotely possible but treason law is very specific," the peer told BBC Radio 4's Today programme.
"I suspect that there are far more appropriate crimes already on the statute book."
Incitement to murder or solicitation to murder, already used in contract killing cases, would stand a better chance of securing a prosecution, Lord Carlile said.
Bakri, the spiritual leader of al-Muhajiroun ("The Emigrants"), said last week that he would not tell police if he knew that Muslims were planning a bomb attack on a train in Britain and supported Muslims who attacked British troops in Afghanistan and Iraq.
British-born Abu Izzadeen, of al-Ghurabaa ("The Strangers") said in an interview that the July 7 bombers were pursuing "mujahideen activity" which would make people "wake up and smell the coffee".
Abu Uzair, a former member of al-Muhajiroun who is now believed to be involved with its successor organisation, the Saviour Sect, said on BBC's Newsnight that after the July 7 attacks "the banner has been raised for jihad inside the UK". He said that Muslims had abandoned a "covenant of security" saying they should not resort to violence in Britain because they were not under threat.
Downing Street refused to be drawn on whether treason charges could be laid.
"There are discussions going on about what would be the appropriate measures to take against individuals," a No 10 spokesman said.
"I am not going to get into discussing whether one charge is better than another. It is important that the right charge is brought.
"It is a question of people looking at the options that they have."