Investors have helped fuel Australia's property boom, but the growth in the rents they charge tenants has hit its lowest annual rate in more than a decade.

Combined capital city rents increased by just 1.8 per cent in 2014. Rents for houses increased 1.2 per cent, while unit rents increased 2.5 per cent during 2014, a CoreLogic RP Data quarterly rental review shows. The slowing in rental growth comes as home values continue to increase in Australian…