The Northern Secretary, Mr Paul Murphy, is to move to plug the loophole that could allow members of the "Real IRA" to avoid being convicted of membership of an outlawed organisation in Northern Ireland.
Mr Murphy was reacting to a decision by Mr Justice Girvan in Belfast Crown Court on Wednesday to dismiss charges of "Real IRA" membership against four Co Tyrone men because, under the Terrorism Act, it was not a proscribed organisation.
Mr Murphy expressed surprise at the judgment as he understood the law was similarly worded in the Republic where "Real IRA" personnel have been convicted of membership of a terrorist organisation.
He said the British government would appeal the decision, and if that failed it would amend the law so that it would be illegal to be a member of the "Real IRA" or Continuity IRA.
"What we will do is appeal this and if necessary we will change the law on it," he said from London in interviews with the BBC and UTV yesterday.
"The term 'IRA', I think, both in Ireland and in the UK, was an umbrella term for all the different groupings within the Irish Republican Army. And it was felt then, it certainly wasn't challenged then, that that covered the 'Real IRA', and that is why it caused everybody to believe this was the case," he said.
"If this is a loophole we have got to cover up, then we'll deal with it. We'll take it to appeal," added Mr Murphy.
His comments may provide some assurances for relatives of the victims of the "Real IRA" bombing of Omagh in August 1998, which claimed the lives of 29 people and twin unborn girls. Mr Michael Gallagher of the relatives' group expressed incredulity that such a loophole existed and demanded immediate rectifying action.
The leader of the House of Commons, Mr Peter Hain, told MPs yesterday that the "Real IRA" should be an illegal organisation.
He said the DPP was forwarding a report to the Attorney General with a view to referring the case to the Court of Appeal.
Mr Justice Girvan, who cleared the four Tyrone men of "Real IRA" membership after declaring it was not a banned terror group, yesterday reserved his judgment until next week on defence demands for their trial to be aborted.
The four, Mr Donald Mullan (33), Firmount Park, Dungannon; Mr Seán Dillon (27), Roughan Way, and Mr Kevin Murphy (33), Altmore Park, both Coalisland; and Mr Brendan O'Connor (26) Cavanoneill Road, Pomeroy, claim they were set up by a missing south Armagh man, Mr Gareth O'Connor.
Mr Mullan, Mr Dillon and Mr Murphy claim they had arranged to do a burglary when allegedly caught red-handed with a rocket-launcher by undercover troops and police in a Co Tyrone field in February 2002.
Mr Justice Girvan will deliver his ruling on Tuesday on the remaining charges of possessing a rocket-launcher and conspiracy to murder.