Secret moves are planned by senior Conservatives to overturn the result of next week's referendum on electoral reform if the country votes to scrap the first-past-the-post system.
They would make a last-ditch attempt in the House of Commons to block a switch to the alternative vote (AV) if it is backed on a low turn-out of electors. No-to-AV campaigners would argue that the result lacked legitimacy because such an important constitutional change should have been approved by a majority of the public.
Under the plan, supporters of first-past-the-post would approach the Commons business committee of MPs, which has the power to set aside time for issues concerning backbenchers.
Although recent polls show the No campaign in a comfortable lead, large numbers of voters still appear not to have made up their minds how – or whether – to vote. The tactic of using the business committee to force a Commons division was successful in overturning moves to give the vote to prisoners.
A senior Conservative MP said last night: "Suppose there was a tiny majority in favour of AV, but only 20 per cent of the country took part in the referendum; people on our side would find it hard to accept. There would be contact with the business committee." He suggested a turn-out of 50 per cent should be required to give legitimacy to a Yes vote – a hurdle that could be impossibly high to clear.
The Government fought off attempts to impose a 40 per cent threshold to make the referendum outcome binding. But a fresh attempt to block a Yes vote in the event of a low turn-out would present David Cameron with a dilemma. He would almost certainly argue that the result should stand, but would face fury among Tory backbenchers.
A survey yesterday showed voters moving decisively against the proposed switch to AV. A ComRes poll for No to AV found the No vote on 45 per cent, the Yes vote on 33 per cent and 22 per cent of voters saying they did not know.
When "don't knows" are excluded, there is a 60-40 margin against the change. A decisive factor in the turnaround appears to have been the attitude of Labour voters, who oppose AV by 61 to 39 per cent.