The index found that in January 2015, newly-let one and two-bedroom rental properties saw the largest growth in rents year-on-year, increasing 3.3% and 1.9% respectively.
Rents on newly-let properties now stand at a UK average of £883 a month, up from £859 a month in January 2014, an increase of 2.8%. One and two-bedroom properties saw the greatest increase in rent, up 8.5% and 3.6% to £751 a month and £810 a month respectively.
In the regions, Greater London saw the largest increase in rent year-on-year, up 10.6% to £1,265 a month, followed by Wales up 6.1% to £666 a month and the South West up 4.1% to £765 a month.
The only region to see a decrease in rent year-on-year was the South East, down 4.1% to £1,035 a month.
Rental arrears have continued to fall in all regions apart from central London and the north of England.
Nick Dunning (pictured), group commercial director at Countrywide, said: “With banks making it easier for landlords to offer longer tenancies and with more competitive buy-to-let mortgage products available, now is an ideal time for landlords to expand their portfolios and provide a more diverse range of affordable rental properties throughout the UK, not just in London and the South East as many would expect.”