The European Elections: Major causes tremors over single currency: Economic policy: Prime Minister says that those who want monetary union now should vote Labour or LibDem

John Major last night invited voters who want a single European currency now to cast their ballots for Labour or the Liberal Democrats. But he refused to close the door on Britain's ultimate acceptance of a single currency under the Tories.

The Prime Minister made it clear it was not a question of principle, but economics: 'I don't know whether it would be appropriate - for me it is an economic question. That is the key point.'

His reply is likely to send a tremor through Mr Major's newly won supporters among the sceptics on Europe who hailed his vision of a 'multi-speed' EU as a turning-point for the Tories. They had hoped it signalled rejection of a single currency. During the current election campaign, Mr Major had appeared to harden his stance on opposing a single currency when he said it was unlikely to come about in his lifetime.

His tone was softened yesterday in a BBC radio interview when he brushed aside the splits in the Cabinet over the single currency, which the campaign has failed to resolve.

'I cannot conceive that it is going to be in our economic interests for a very long time,' Mr Major said. 'When it is, I have kept the point open for the British Parliament to consider in the light of the circumstances at that time.'

'I don't know what they will be. I don't how big the community will be. I don't know which members will be ready to go forward. I don't know what the impact of it would be at that stage. I don't know what the alternatives are and neither does anyone else. That is why it is folly at this stage to decide whether it is right or wrong.'

Mr Major insisted his position on the single currency had remained the same 'right the way through', after opting out of the decision in the Maastricht treaty.

'If you believe we should agree now to a single currency, then vote Labour or the Liberal Democrats,' he said. 'If you believe you should wait and see whether it is practicable, vote Conservative.'

Last night in his final campaign speech, the Prime Minister attacked the 'seven deadly sins' of the Labour and Liberal Democrat parties.

He told a rally in London that Labour and the Liberal Democrats supported more regulation while the Tories stood for de-regulation; they wanted the Social Chapter and the single currency without leaving it to Parliament to decide; the European Socialist manifesto called for taxes to be levelled up while the Tories wanted to keep taxes 'as low as they can be - and when we can we'll get them down again'; they wanted to put up Community spending and renegotiate the rebate.

'The veto, more power to Brussels, the Social Chapter, single currency, taxes, spending, and the rebate - those are the issues this election is all about,' the Prime Minister said.

The Liberal Democrats, who have no MEPs, were damping down their prospects of gains in tomorrow's polls. According to their private predictions, they will not get more than four seats.

Top of their target list is Somerset and Devon North, where they need a 2.4 per cent swing, Cornwall and West Plymouth (needing a 3.4 per cent swing), Devon and East Plymouth (an 8.5 per cent swing), and Itchen Test and Avon (13.8 per cent).