OBR calls in cyber expert over botched release of Budget analysis

The unexpected release caused a reaction in the Commons chamber as Prime Minister's Questions (PMQs) started, with Reeves seen looking at her own phone with concern, before Treasury Minister Torsten Bell, who was sitting behind her, passed his mobile phone to her as the news broke.

Notes were being passed down the row of cabinet ministers before the Chief secretary to the Treasury James Murray held his phone in front of Reeves and she copied down some words onto the top of what seemed to be her Budget speech.

Conservative MPs quickly started posting pages of the document on social media and Tory frontbenchers, including shadow chancellor Mel Stride, were seen whispering and making notes.

Stride then called a point of order at the end of PMQs to demand an inquiry into the leak, saying: "It is utterly outrageous that this has happened and this leak may constitute a criminal act."

There have already been weeks of leaks and speculation over policy to the media in the run-up to the Budget, which the chancellor was reprimanded for by deputy speaker Nus Ghani.

Although this is the first time the OBR has made this sort of mistake, it is not the first time parts of the Budget have leaked out before they should have done.

Back in 2013, the Evening Standard mistakenly published details of George Osborne's Budget before he got to his feet in the Commons, including details of major announcements on tax.

The then-Labour leader Ed Miliband was reading a photocopy of the front page as Osborne spoke and said the chancellor "almost need not have bothered coming" to the Commons.

In 1996, the Daily Mirror was sent the full contents of Chancellor Ken Clarke's Budget in advance of his speech.

Piers Morgan, who was the paper's editor at the time, only published some details in the next day's paper, sending the rest back to the Treasury.

At the time, prime minister John Major ordered a leak inquiry and the Metropolitan Police investigated, but no one was arrested.

In 1947, the Labour Chancellor Hugh Dalton was forced to resign after giving a journalist details of the Budget before making his statement.

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