ED Miliband is too weak to sack "nightmare" Ed Balls, senior Conservative Grant Shapps said after leaked emails revealed apparent Labour tensions.

The Tory chairman said Mr Miliband's adviser's disparaging analysis of the shadow chancellor proved that Labour could not be trusted on the economy.

Mr Shapps said the emails, in which one of the Labour leader's advisers calls Mr Balls's response to optimistic economic growth forecasts a "nightmare", showed Labour had not moved on from the in-fighting seen in the Tony Blair and Gordon Brown years.

He said: "Miliband never wanted Balls in the post, but if he's too weak to sack his 'nightmare' shadow chancellor, then he is too weak to cut the deficit, too weak to fix the welfare system and too weak to stand up for ordinary hard-working people. Once again we're seeing in-fighting between a Labour leader and his shadow chancellor."

In the emails, obtained by a Sunday newspaper, Mr Miliband's adviser Torsten Bell describes Mr Balls's response to this week's optimistic growth, jobs and inflation forecasts from the Bank of England as a "nightmare".

Mr Bell seemed to take issue with the briefing from the shadow chancellor's camp which argued for a "recovery built to last" and focused on "cost of living" and an "economy that works for working people".

Shadow health secretary Andy Burnham said the Labour Party and its front bench was more united than it has been in 20 years. He said the media was "scraping the barrel" over the emails.