The average landlord’s portfolio now features 11.1 properties - up from 10.2 in November last year.

Figures released by financial services firm Paragon also highlight that average portfolio values have risen by 7% between November 2006 and February 2007.

John Heron, managing director of Paragon Mortgages, said: “Landlords are able to extend their portfolios through good yields and rental incomes, generated by increased tenant demand.”

The number of properties owned by each landlord is predicted to rise further over the next 12 months, with those surveyed expecting an 8% increase across their portfolios.