The Tories have attempted to steal the chancellor's thunder by announcing they would adopt his golden rule and have it independently verified by the National Audit Office.

The move is being seen as an attempt to undermine what the Conservatives see as Gordon Brown's position as both judge and jury on his own tests.

The party claims Brown has used statistics to mislead voters over the real state of his finances.

However the announcement could restrict the scope for tax cuts under a Tory administration.