When George Osborne walked into the Commons chamber yesterday afternoon, he knew almost everything the Chancellor was about to say.

Having read an advance copy of the speech in the Shadow Cabinet room earlier, he knew about Alistair Darling’s plans to lower VAT to 15 per cent, raise taxes on high-earners and plans to expand lending to small businesses. However, under a convention that allows the Treasury to withhold market-sensitive information, two passages had been blacked out of their advance copy.

The first was a declaration that the Tories’ plan did not amount to an “action plan”.

The second was Mr Darling’s attempts to steal back the Tory’s favourite gibe. The Government had refused Mr Osborne an advance look at the passage that read: “We did fix the many roofs that needed fixing – the roofs of schools, hospitals and homes throughout the United Kingdom.” A source in Mr Osborne’s office asked: “Did they really think that political gibe was market-sensitive?”

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There were some suspicions that the Conservatives had received more advance notice than they would admit to. Leaks over the weekend about the Pre-Budget Report, with the news of the VAT cut emerging on Sunday morning and new top-rate tax band yesterday, fuelled rumours that the Tories may have seen an advance copy.

There is a widespread belief that the Tories had advance notice of last year’s inheritance tax move in the report, prompting Mr Osborne to announce their own cut during the Conservative conference.

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