But what can we tell the voters?

WITH the Maastricht treaty due for its long-postponed Commons denouement this week, a story told by a senior minister comes to mind. Finding himself in an unfamiliar Commons corridor, he saw the unmistakable figure of a prominent Maastricht rebel bearing down on him. Unable to face another protracted discussion, the minister took evasive action, swerving through a nearby doorway. To his surprise, one of John Major's most loyal lieutenants passed an uncomfortable few minutes in a Commons cupboard.

This week much of the nation may feel a similar urge to hide as the Commons embarks on its hideously complex vote on Mr Major's Social Chapter opt-out. The whips predict a close result, but one is tempted to ask how they could know. The arithmetic would be complicated even if potential rebels were willing to reveal their hands - which they are naturally reluctant to do since this would invite trouble from party managers and constituency loyalists. And, as the Government's fate is sealed, an orgy of tactical voting, perverse even by the standards of the House of Commons, will complicate things further.

Opponents of the Social Chapter may vote for it to try to scupper the Bill. Supporters of it will vote against in order to try to save Maastricht. All this over a Bill which a majority of the Commons - more than half of the Conservatives and Labour, and all the Liberal Democrats except one - wants on the statute book.

How has the Commons got into this fix? The threat to Mr Major comes from hardened Euro-sceptics so opposed to the Maastricht treaty they may vote for the Social Chapter in the hope of making it politically impossible to ratify the treaty. Their difficulty is that, despite repeated questioning, Mr Major has refused to say what he will do if the Commons votes for the Social Chapter he has so vigorously opposed. Legally he could flout the will of Parliament, but the political consequences would be grave; and many senior Tories believe that he would risk splitting the party by embracing the chapter instead.

Even if Labour's Social Chapter amendment is seen off the danger is not over. Maastricht can come into force only 'when each House of Parliament has come to a Resolution', so a defeat on the Government's own motion would dispatch the treaty temporarily to limbo.

No wonder Sir Teddy Taylor, the Euro-rebel who produced a four-page guide to voting possibilities, concluded it with a plaintive section entitled: 'But how can we explain such a complex series of events to others?'

Last November Mr Major survived a crucial Commons division in the paving debate for the Maastricht Bill with a majority of just three. Since then, the unexpected deaths of Judith Chaplin and Robert Adley have cut his reliable vote. Nor would one expect Edward Leigh, the junior minister sacked by Mr Major for disloyalty over Europe, to have too many scruples about causing the Government discomfort.

This weekend, Conservative Central Office will be doing what it can to get local parties to apply pressure on their MPs to uphold that most sacred of Tory tenets: loyalty to the leader. But, with mounting discontent over the Government's performance, meddlers from London have to tread carefully. As one party worker put it: 'Constituency chairmen are quite likely to turn round and say the party is completely out of touch with the mood of the voters.'

Nevertheless, it is in the interest of the potential rebels to keep their strategy opaque. The mood in the Great College Street office inhabited by the lanky William Cash and his assorted Euro-sceptic colleagues has been slightly deflated by the lack of progress in the House of Lords.

For Conservative sceptic MPs the moment of truth is at hand. Potential rebels, numbering up to 12, will divide broadly into two camps: the hardened opponents like Mr Cash, James Cran, Sir Teddy, and Nicholas Winterton, who might be willing to vote tactically for the Social Chapter; and the softer rebels who would find this course of action impossible to justify to their consituency associations. This second group will be more willing to vote against the Government's motion - which merely 'notes' its opposition to the Social Chapter - than to vote for Labour's amendment to remove the British opt-out.

The small band of Conservatives who actually believe in the Social Chapter, which includes Sir Edward Heath and Hugh Dykes, also faces a dilemma. They, too, are expected to vote tactically - against Labour's Social Chapter amendment. The treaty, they argue, must come first.

With Labour and the Liberal Democrats firmly behind the Opposition amendment, everything depends on the votes of the minor parties, particularly the Unionists. The one firmly anti-EC group in Parliament may decide the fate of the treaty, the Social Chapter opt-out, and possibly Mr Major's premiership.

The Unionist instinct is staunchly anti-Brussels: take, for example, the famous 1984 sermon from the Democratic Unionist the Reverend Ian Paisley, which vented suspicions of Catholic expansionism in Europe. What, he asked his congregation rhetorically, 'holds the Common Market together? Satanic power'. There are shades of opinion among the nine more moderate Ulster Unionists, and unofficial contacts between them and senior Conservatives will probably go up to the wire.

Left to themselves, maybe four would vote against the Government, two with it, and three would keep an open mind.

In the run-up to the paving debate last year, ministers were preparing to concede a select committee for Northern Ireland in exchange for Unionist support. But negotiations never got under way because it became apparent that the nine Unionist MPs would vote against the Government.

The select committee will be on offer again, although it is unlikely to be enough. Not even the Unionists expect Mr Major to depart from the Government's support for the Anglo-Irish agreement. However, a desperate government might promise to renegotiate the agreement, or put more pressure on the Irish government to abandon its constitutional claim to the island of Ireland. On the subject of security - of increasing concern in the province - the Government has little to offer: at best the Unionists might hope for a greater consultative role.

Jim Molyneaux, leader of the Ulster Unionists, is thought to have spoken already to Richard Ryder, the Chief Whip. There are echoes here of the 1970s, when Jim (now Lord) Callaghan invited Mr Molyneaux to Number 10, declaring later that co-operation between the government and the Unionists was 'excellent'. Mr Major is unlikely to be as lucky. Abstentions are probably the best he can hope for.

The entire spectacle reflects poorly on Parliament, on Europe and on the already battered image of our politicians. To many voters, it looks irrelevant compared with issues like the economy and taxation. The final irony for Mr Major is that his negotiating triumph of 18 months ago appears increasingly insignificant as Europe's agenda slips away from that of 1991. Yet Maastricht has clogged up Mr Major's Parliament for a year, and split his party. It could still precipitate his downfall.