British requests for military helicopters to be allowed greater freedom to cross the border while on anti-terrorist operations have been rejected at official level by the Irish because of the issue's political sensitivity.
Dublin, which is arguing against any over-reaction to last week's terrorist action, is also opposed to more cross-border co-operation over 'hot pursuit'; increases in its intelligence operations; and to any greater deployment of its security forces close to the border. The Irish government points out that it already spends more per head of population on security than Britain.
Pressure is mounting for tougher action and critics have not been satisfied by a joint statement from John Major and the Irish Prime Minister, Albert Reynolds, on Friday, pledging to 'carry forward the close co- operation on security matters' and to 'continue their intensive efforts to deal with terrorism'.
Senior security officers were yesterday discussing plans to deploy troops with armoured vehicles to patrol British airports for the first time since the Gulf War. In an interview in today's Sunday Express, Mr Major says that the option of internment in Northern Ireland has not been ruled out.
Mr Major says that hardliners may be trying to provoke a break-up of the joint declaration to 'let them off the hook.'
He adds: 'They have seen the dangers of splitting before and I suspect these attacks are to try to reinforce the unity of the movement in some perverse and irrational way so it may be that they are not going to respond directly to the offer that lies before them to give up violence.'
But in the aftermath of last week's mortar attacks on Heathrow airport and of the failure of the IRA to respond to the Downing Street Declaration, the Ulster Unionists and a senior Conservative backbencher yesterday called for the return of internment, north and south of the border. That prospect was categorically rejected by Mr Reynolds last year.
Ken Maginnis, security spokesman for the Ulster Unionists, called for tighter cross-border security and a 'very selective form of internment which would disable the IRA's command structure'. He added: 'If the governments do not look carefully at the likely consequences of blatant defiance by the IRA, there is very little credit due to them.'
Andrew Hunter, chairman of the Conservative backbench Northern Ireland committee, told Radio 4's Today programme: 'We could round up three quarters of the IRA by breakfast tomorrow with internment. It is on the agenda but it does need the support of the Republic of Ireland.'
Last December Mr Reynolds warned of a crackdown if the declaration were to be finally rejected. He said: 'Undoubtedly there would be stiffer security situations. After a period in which such strong support has been expressed by people in both communities for peace, there would be revulsion at a resumption of full-scale violence again.'
But Irish officials now urge caution, emphasising that an over-reaction to the events of last week would play into the hands of the IRA.
Senior British sources said last week that the IRA may be attempting to 'shake our confidence in the joint declaration' through its mortar attacks. But some senior Conservatives are pressing for a wholesale rethink of policy. Backbenchers too are restive at the lack of any British initiative, either on security or on constitutional talks.
One leading Tory said yesterday that the Government's policy had been left in 'limbo' after the show of defiance by the IRA at Heathrow on Thursday and Friday.
The peace process is now seen as dormant, with the IRA apparently intent on continuing the armed struggle and the Ulster Unionists' decision to break off their participation. Ministers believe that, for party political reasons, no progress with the Unionists will be possible before the European elections on 9 June.