Northern Ireland's First Minister, Mr David Trimble, has denounced as "a constitutional monstrosity" the British government's determination to proceed with plans to allow members of the Oireachtas to sit in the Stormont Assembly or Westminster.
The plan, which unionists think is designed to enable Sinn Fein eventually to sit in government on both sides of the Border, was defeated last week in the House of Lords. The government will introduce the original Clause 1 of the Disqualification Bill in the Commons this afternoon.
However, as ministers rush through their remaining programme ahead of the dissolution of the present parliamentary session, timetable problems suggest an outside possibility that the measure might fall.
In that event, government sources say they will bring it back in the new session opening on December 6th.
Meanwhile, Mr Trimble was facing further defeat in the Commons last night, as ministers signalled their determination to exempt Northern Ireland parties from new legislation banning foreign funding of political parties in the United Kingdom.
Mr Trimble and the Conservative leader, Mr William Hague, were resigned to the defeat of a series of amendments seeking to extend the legislation to Northern Ireland.
The Ulster Unionists have argued on the principle of UK-wide application, while the Conservatives were also pressing at least for amendment to the legislation which would prevent foreign funding of any referendum on Northern Ireland's constitutional future.
The Tories argued that the Political Parties Elections and Referendums Bill would also enable dissident republicans to benefit from US funding.
The legislation follows the recommendations of the Neill Committee that foreign funding be banned and that parties in the UK be required to keep detailed records, identify all donors of more than £5,000 sterling and report to the new UK Electoral Commission.
However, the government has argued that "special factors" in relation to Northern Ireland justify the exemption, initially to last for four years.
The Tories also say one "bizarre" consequence of the legislation is that political organisations not registered as parties would be denied the same exemption.