The government’s Budget has been revealed early after a blunder by the Office for Budget Responsibility meant its full analysis was published before Chancellor Rachel Reeves was due to begin her speech.

The document, which normally appears only after the Chancellor has finished speaking, was released before midday.

It sets out the entire package of tax and spending measures that Reeves is expected to confirm in the Commons this afternoon.

The OBR has blamed a “technical error” for the early publication, adding that it has launched a full investigation.

Among the measures confirmed in the OBR’s analysis is a new surcharge on homes worth more than £2 million.

The change amounts to a form of mansion tax, raising an estimated £400 million for the Treasury.

The move is likely to affect ow

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