Nick Robinson said he had been told the decision to refuse the Tory request - made in February - was taken by the Cabinet Secretary Sir Gus O'Donnell, not by ministers as following standard pre-election meetings between opposition parties and civil servants.
But he said the question of which party was being the most upfront and honest about spending was likely to dominate debate in the run-up to the election.
Chief Secretary to the Treasury Liam Byrne said Mr Osborne's comments were designed to "distract" from the cutbacks he was planning if elected.
"It is utterly misleading for George Osborne to claim that the prime minister prevented the Tories getting information," he said.
"The prime minister agrees the process to allow the shadow cabinet to meet with senior cabinet officials but he has played no part in and received no report of any of those meetings."
Earlier, Mr Byrne said it would be "unwise" to make spending predictions for the period after 2011 - the last year for which Labour has set out plans - because of uncertainty over the economic situation.
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