Errors have been found in the weighting of goods used in the basket of items for the retail price index of inflation that underpins payments on inflation-linked government bonds.
The Office for National Statistics has discovered that March’s rate of RPI inflation should have been 2.5 per cent rather than 2.4 per cent.
Statisticians also said June’s RPI should have been 2.8 per cent rather than 2.9 per cent.
RPI underpins payments on billions of pounds’ worth of inflation-linked government bonds.
Unlike other statistics, RPI is not corrected retrospectively. The discovery of the error will lead to a “discontinuity” between the level of the RPI index in June’s data and that in the next release, which covers July.
The ONS has said for several years that RPI “no longer” gives an accurate measure of inflation.
It confirmed the separate consumer prices index of inflation, which is targeted by the Bank of England, was not affected by the error.
RPI is widely used in commercial contracts as well as for British government bonds.
Earlier this week, Ian Diamond was appointed as national statistician. He succeeds John Pullinger, who retired at the end of June.
The national statistician is chief executive of the UK Statistics Authority, permanent secretary of the ONS and head of the Government Statistical Service.
Diamond previously held the role of chief executive of the Economic and Social Research Council.
He said: “The UK’s statistical system is one admired world-over and it is an enormous privilege to have been appointed as the UK’s national statistician. I’m looking forward to building on the work of John Pullinger, as we make use of rich new data sources to deliver the data decision-makers across the UK need.
“I’m particularly excited to be working with staff across the Office for National Statistics and the Government Statistical Service, as we empower our partners in parliament, academia, business and beyond with trusted and quality data.”