The spending watchdog’s decision comes after fears the sell-off, which priced the shares at 330p, could have undervalued them.
The National Audit Office said it would look at how the price range for the share offer was set and the discussion of possible revisions to the range.
“Given the scale and significance of what has been the first public offering for many years of shares in a publicly owned company, the National Audit Office will be conducting a value for money examination of the privatisation of the Royal Mail,” the spending watchdog said in a statement yesterday.
The outcome of its investigation is expected to be published in Spring next year.
Royal Mail shares closed 7.6 per cent higher yesterday at 537p.