The East of England and East Midlands recorded the greatest increase of over 50s at 3% year-on-year followed by Wales and London up 2%.
The significant decline in tenants aged under 25 is greatest in Wales where there has been an 8% decrease followed by the South West and East of England (-3%) and South East (-2%).
Nick Dunning, group commercial director at Countrywide, said: “Renting a property was previously a choice for the younger generation as they saved for a few years to get on the housing ladder. However there is currently a demographic change in the UK rental market with people renting for longer and in some cases for life.
“Reasons vary and for some it is because they cannot afford to save a deposit to buy their own home but others choose to rent and enjoy the flexibility it gives them especially in terms of job mobility.”
The index showed that tenants aged 41 and over now equate to nearly a third (29%) of all of those renting a property through Countrywide in England, Scotland and Wales and Countrywide predicts this figure is likely to rise in the future.
The average length of tenancy is now 19 months in the UK, a slight increase on 2012. Central London has the highest length of tenancy at 22 months and Wales the lowest at 14 months.
With families making up a third of tenants renting a property through Countrywide, the decision by Nationwide to extend the tenancies will give long-term renters more security.
The average monthly rent increased 1.1% year on year in quarter two of 2013 to £845 a month. Scotland saw a 6.7% rise in average monthly rents in the same period, the greatest increase of any region.
Yields remained strong across England, Scotland and Wales with Wales seeing the highest yield at 6.6%, followed by the Midlands (6.5%) and the North (6.4%).
Arrears fell on average by 0.8% year on year but increased in Scotland 2.4% and Wales 2%.
Dunning said: “Renting is a flexible and relatively hassle-free way of living which suits many people's lifestyles. It allows them to settle in a location where perhaps they couldn’t afford to buy but they enjoy living in.
“However with a growing population of lifetime renters and more 18 to 25 years olds having to live with their parents for longer because they cannot afford to rent or buy, increasing the amount of good quality, affordable rental accommodation is needed to meet this demand.”
He added: “With banks making it easier for landlords to offer longer tenancies, more competitive buy-to-let mortgage products available and demand for rental accommodation outstripping supply now is an ideal time for landlords to expand their portfolios and provide a more diverse range of affordable rental properties.”
