Less than a third of households in private rented accommodation are there by choice, according to housing charity Threshold.

Threshold's Tenant Sentiment Survey shows that the remaining 71% are there because they cannot afford a mortgage to buy a property or get social housing.

The survey was carried out in April on more than 300 tenants who had used Threshold's service.

Threshold Chief Executive John-Mark McCafferty said the data showed that one in seven tenants spent at least half of their income on rent.

Speaking on RTÉ’s Morning Ireland, he said some respondents said their rent had increased by more than 4%, showing that some landlords are ignoring rent pressure zones.

Mr McCafferty said there needs to be stronger enforcement of the regulations.

He said Threshold deals with over 20,000 tenants a year and this survey highlighted some of the issues facing them, including affordability, quality and insecurity.

The survey, to mark Threshold's 40th anniversary, found that 96% of tenants found it either difficult or extremely difficult to find rental accommodation.

It found that 70% of tenants have been renting for five years or longer and 44% of tenants still expect to be renting in five years' time.

47% of tenants said they felt insecure in their tenancy.

31% of tenants had experienced a rent increase in the previous 12 months, with 65% of those saying the rent had been increased in excess of the 4% Rent Pressure Zone cap.

The UN Special Rapporteur for Adequate Housing said housing needs to be a constitutionally protected right. 

Leilani Farha said homelessness is a global phenomenon and, with the exception of Finland, is rising.

She said housing is a human right and is enshrined in human rights law so it should not be viewed as a commodity. 

She said in Finland housing is constitutionally protected and "seen as a place of dignity where tenants are protected".

But she said while constitutional protection is a good first step it is not the answer to the crisis. 

Ms Farhi said it is also essential that those rights are implemented.