An employee of the Treasury has accidentally emailed confidential inflation figures to nearly 400 people, it has emerged.
The figures for April were sent in error to ministers and advisers, before their official release. The data revealed that inflation has risen to 4.5 percent.
The fact this was the second such instance prompted Statistics Authority chairman Sir Michael Scholar to write to the chancellor.
In his letter, Scholar wrote that current procedures ahead of official data releases were allowing politicians time "to spin".
"Why do 50 or more people need to have the [consumer price index] a day ahead of the opposition, parliament, the public and the media? There is, I believe, no good operational reason," he wrote.
Scholar warned of the "risk of market manipulation if key economic data fall in to the wrong hands before publication".
A Treasury spokesman said: "This was an accidental breach by the official side of the Treasury. No ministers were involved and no one made personal or political profit from this mistake."
The Treasury said it has put in place "stringent measures" to avoid the problem happening again.