Tim Holt, ONS director, blamed limited resources for the failure to address until this autumn deficiencies in the average earnings growth figures - one of the most important pieces of information used by the Bank of England's Monetary Policy Committee in setting interest rates.
He told MPs on the Treasury sub-committee: "[Revisions to] earnings were given a lower priority. If we'd had the resources, we would have done the work a year ago." He added: "There may have been a problem of not having the right intellectual resources in the right place at the right time."
The ONS head also blamed deficiencies in the data series that his agency - set up three years ago - inherited from the employment department. "The old series had not really been updated. There was no doubt that the methodology being used was not best practice," he said.
Recent revisions to the earnings data appalled the Bank and the Treasury. It is feared that the MPC may have wrongly raised rates in June on the basis of the original data from the ONS. An inquiry headed by senior Bank and Treasury figures into the shock revisions has been launched.
However, Mr Holt said yesterday that the MPC, like other users of the data, "fully understands the margins of error" involved. He added that the market-sensitive nature of the earnings figures made it difficult to discuss fully possible implications of the data revisions with the Bank.
It would not be right, Mr Holt said, for the Bank to make interest-rate decisions on the basis of information that had not been released to the markets.
The ONS chief defended his staff in Runcorn who put together the labour market data. He said: "The professional commitment to what we do pervades the whole office. That commitment is strong in Runcorn."
However, an ONS insider said: "That lot in Runcorn are changing the figures constantly. It's a real can of worms up there. No-one should believe any of the figures they publish."
On Monday Mr Holt said he would be suspending publication of the earnings data until a review of the revisions had been completed. "Public confidence in this series has clearly been dented," he said.
Outlook, page 23