The clouds gather over Osborne, with six weeks to go until the Budget

Osborne: Storm clouds gather for a beleaguered chancellor

Osborne: Storm clouds gather for a beleaguered chancellor

George Osborne was the subject of another whispering campaign today, as the chancellor was increasingly singled out for criticism for Britain's economic stagnation.

Senior political figures from inside the Conservative party criticised Osborne for his decision to freeze the inheritance tax threshold until 2017, amid disastrous poll ratings.

Former Cabinet minister and adviser to Osborne Lord Forsyth called the decision to freeze the threshold at £325,000 "unfair" and "very disappointing", especially considering the chancellor pledged to raise it to £1 million before the election – in a move which scared Gordon Brown off holding a snap election.

Leading backbencher David Davies said the move would "impact ordinary people".

The latest round of criticism of the chancellor is increasingly public, as patience with his economic programme starts to wear thin.

When Osborne first made the inheritance tax pledge in 2007, he boosted Tory poll ratings by five points, almost overnight. That contrasts unpleasantly with the Guardian/ICM survey released yesterday, which put the Tories on 29% – roughly the level the Tories reached during the John Major years  – and Labour on 41%.

Confidence in Osborne was battered by last year's Budget – later given the moniker the 'omnishambles Budget' after several of its policies had to be reversed.

Osborne now has six weeks to prepare for this year's Budget and Tory backbenchers are increasingly keen to demand the implementation of right-wing economic policies to stimulate growth.

Many want movement on the married couples' tax breaks, although the introduction of the policy would further distance the Tories from their Liberal Democrat colleagues.

Others are supporting a proposal by backbench MP Robert Halfon for the reinstatement of the 10p tax rate, which could get the parliamentary party back onside and put Labour on the back foot.

The 10p tax rate was scrapped by Brown so it's reintroduction would serve as an uncomfortable reminder to Labour of a less-than-impressive period from its past, while also showing the Tories reducing taxes for low earners.

The Halfon proposal would apply to earnings between £9,205 and £12,000 and cost £6 billion.

There was further criticism of Osborne today after it was revealed that just one fifth of the infrastructure projects in the national infrastructure plan are being built. In terms of completion rates, just one in seven projects have been finished.

Business secretary Vince Cable told the Financial Times the chancellor should borrow more to fund increased capital spending.