The shadow defence secretary, Iain Duncan-Smith, has promised to scrap the treaty agreed at Nice in the small hours of Monday morning.

Promising to put the issue to the British people, Duncan-Smith said that if the treaty was unratified when a Conservative government was next elected, his party "will take the view that it is integrationist and will not pass it through".

The move will dismay pro-Europeans in the party. In an exclusive interview with ePolitix.com on Friday, the former Conservative chancellor, Kenneth Clarke, warned Tories against a "pointless" hostility to Nice saying: "I think it's pointless to be too hostile. I don't understand how you can be in favour of enlargement but against treaty changes of the obvious kind at Nice. I think we need a new treaty, we need agreement on the size of the commission, we need an agreement on the weighting of votes and we need a bit more qualified majority voting. It's no good to turn around and say we are in favour of enlarging to central and eastern Europe but we are not going to ratify the treaty that makes it essential to pave the way to get there."

Duncan Smith, however, believes the Nice agreement will be divisive in the long term. "It is simply the wrong thing for Europe to be doing at this stage. To have more areas where the majority can impose their will on the minority is divisive. It breeds discord, not harmony - it breeds division not unity."