The government’s Office for National Statistics is introducing a new way of measuring rent rises from the spring.
It will double the sample it uses from 250,000 rents to about 500,000 a year.
Analysts say that had the new sample been used in recent years it would have reflected slightly higher rent increases than those officially recorded by the ONS.
The Financial Times calculates that average annual growth in rents between January 2016 and October this year would be 2.8 per cent rather than 2.1 per cent.
That would have lifted the average annual growth in the overall Consumer Prices Index from 3.4 to 3.5 per cent over the same period.