The latest market research from the Association of Residential Lettings Agents (ARLA) reveals an upward trend in landlord investment over the past 12 months.

The average number of buy-to-let properties owned by landlords peaked at eight in the final quarter of 2012, up from seven at the beginning of the year. The apparent rise in confidence in the market also prompted increased landlord activity, with 29% of survey respondents stating they have bought a property in the past year compared to 25% at the start of 2012.

The rise in landlord confidence is also reflected in the jump in value of buy-to-let mortgages, with an 8% increase in the final quarter of 2012 totalling £4.2 billion according to the Council of Mortgage Lenders (CML).

Ian Potter, Managing Director of ARLA, said: "The latest data from ARLA suggests that landlords are carefully but concertedly increasing their portfolios and activity is returning to the buy-to-let market. Whilst many investors naturally remain cautious, the climb to an average of eight properties per landlord shows that 2012 was a strong year for the Private Rented Sector."

Despite wider economic uncertainly, the latest ARLA data indicates that rental properties continue to be attractive investment prospects for landlords, driven by increased consumer demand as consumer home ownership levels decline.

Potter added: "The PRS will continue to be a home for investors throughout 2013, and strong tenant demand coupled with affordable house prices in some areas will help to sustain the sectors growth. It also means there is increased need for higher standards in the sector, to ensure the growing number of tenants and landlords are protected."