Details of a massive overspend on Britain's spy headquarters are set to be published.

Tony Blair has indicated he will allow limited publication of two highly critical secret reports revealing how spending on the headquarters buildings of the MI5 and MI6 spymasters overran by almost £226m.

The reports, by the National Audit Office spending watchdog, highlighted how the cost of MI6's futuristic headquarters building on the banks of the River Thames at Vauxhall Cross in London, escalated from an initial estimate of £22m to an eventual bill of £81m.

And it also reported on the overspend on the refurbishiment of nearby Thames House for MI5, which rose from a provisional estimate of £60m to £227m.

The government's change of heart follows strong criticism by the Parliamentary Intelligence and Security Committee over the government's refusal to allow the release of the reports.

In its annual report last year the committee, which oversees the work of the secret services, said it did not believe publication would in "any way prejudice national security" as the government had argued.

However the Prime Minister, in his official response to the committee's report, said that parts of the documents remained sensitive and that he could not allow full publication as the committee was demanding.

"They contain some sensitive information and the government's view remains that they still could not be published in full without damaging agency security," he said.

Instead he said the government would consult with the chairman of the Commons Public Accounts Committee, Tory MP David Davis, as to what changes needed to be made to make the reports "fit for publication" by the NAO.

Mr Davis welcomed the Prime Minister's announcement, saying government secrecy should be confined to issues which were "genuinely secret in nature".

He said: "I have worked closely with the various intelligence and security services in the past and am fully aware of the need for operational secrecy on appropriate matters. But there is a great deal of information that could and should be put into the public domain."

"Last year, the government agreed that the makers of the Bond movie could use the MI6 building as a backdrop, so its existence and location are hardly secret.

"If this is good enough for the entertainment industry, a little more disclosure is surely good enough for the British public."