Nick Clegg signals new distance from 'fantasy world' Tories

Nick Clegg will launch the pre-election process of distancing his party from the Conservatives on Monday, depicting one of the Liberal Democrats' key roles in the coalition as preventing the Tory right from pursuing a "fantasy world" outside the European Union.

In effect setting out his party's platform for the 2015 general election, the Lib Dem leader will claim that his party has proved its worth as a force that can anchor governments to the centre ground, navigating between the equally undesirable ideologies of left and right. His remarks will signal a big shift from the early phase of the coalition, when Clegg emphasised the need for the Lib Dems to "own the coalition" jointly with the Tories, rather than seeing themselves as fighting endless battles with David Cameron's party.

Clegg will say that Lib Dems have learned to temper their own "dogmatic liberalism" to the requirements of government and practise a "pragmatic liberalism" that allows them to make often necessarily "invidious choices", such as those over welfare cuts, to bring spending under control.

While the two parties will present a new coalition agreement in the new year, Clegg will make clear the programme will be the product of creative tension rather than shared goals. "Our offer is different from the Conservatives'," he will declare, stating that the Lib Dems can be become a "permanent fixture of government" only if they accept the need for uncomfortable compromises. The alternative will be the "irrelevance of opposition".

Clegg will say: "The Tory right dreams of a fantasy world where we can walk away from the EU but magically keep our economy strong; where we can pretend that the world hasn't moved on and stand opposed to gay marriage; where we can refuse to accept the verdict of the British people and pretend the Conservatives won a majority of their own."

His remarks come as the Tories also prepare to begin their first general election meetings early in the new year, with new campaign chief Lynton Crosby taking the lead role in planning. George Osborne will still be involved but, according to officials, on a less "day-to-day" basis than the Australian who masterminded Boris Johnson's re-election as London mayor.

Osborne faced strong criticism from Labour, particularly after his botched budget in May, for being a "part-time chancellor" who was distracted by having a second role as strategy chief. While Cameron and Osborne will be in ultimate charge, the role of Crosby, Tories say, will help to deflect such accusation against Osborne in future.

Both the Tories and Lib Dems, who are languishing on just 8% in Sunday's Opinium/Observer poll, have long accepted that phase two of the coalition will involve some "decoupling" as they try to reassert their own strong identities in the run up to 2015. But rows over Europe and constitutional reform in particular have bought the extent of differences to the surface earlier than many expected.

Clegg will say Labour – with whom his party would have to consider forming a coalition if Miliband's party wins the most seats in 2015 but fails to gain an overall majority – "lives in a different but no less destructive fantasy world where their irresponsible borrowing can be remedied by borrowing more; where every budget reduction can be opposed without explaining where the money should come from; where games can be played with political reform and EU budget policy without long-term damage to their credibility."