About half of tenants in receipt of rent supplement have to “top-up” to meet their rent, and three quarters of these are households with children, successive surveys by the housing charity Threshold indicate.

Threshold chief executive Bob Jordan said rent supplement rates were now so far short of what it actually cost to rent a home that tenants in receipt of the payment were having to go without food and other essentials in order to “top-up” enough to meet the asked-for rent.

“The rent supplement scheme is not fit for purpose,” he said.

The practise of “topping-up” rent supplement is illegal but has long been thought to be widespread. It occurs when the rent supplement allowance, paid by the Department of Social Protection to private sector tenants dependent on social welfare, is insufficient to pay the rent. Though tenants are expected to pay up to €30 from their welfare payment towards the rent, they are not meant to contribute any more.

Threshold surveys since 2012 indicate tenants are paying far more in order to keep their home.

According to the most recent survey conducted in June, of 133 rent-supplement dependent clients of the charity, 44 per cent (58 people) were “topping up”.

A survey of 125 rent supplement clients conducted in January, found 47 per cent per cent were making extra payments, while a survey in June 2012 of 100 clients found 55 per cent were “topping up”.

“Two thirds (67 per cent) of those [in the 2012 survey] said making extra payments affected their spending in other areas,” said Mr Jordan. “In Threshold’s survey 74 per cent of tenants who were topping up were couples or lone parents with children.”

Speaking at the publication of the organisation’s “pre-budget advisory on rent supplement”, Mr Jordan called for an immediate increase in the rent caps, combined with some form of rent control to offset any risk rents would increase as a result. He said renters at the lower end of the market were paying the price of Government inaction on controlling rents, and too low rent supplement rates.

“These tenants face extreme difficulties in finding suitable accommodation they can afford. They must battle against discrimination as many landlords tend to favour working tenants, and now, due to spiralling rents many are currently struggling to hold on to their homes.”

While average rents increased by more than 10 per cent in Dublin and about three per cent outside Dublin in the second three months of the year compared with the first three, Mr Jordan said tenants at the lower end of the market were seeing their rents increased by up to 40 per cent and even 50 per cent when it came time to renew the lease.

In addition to increased rent supplement rates, Threshold is calling for an extension of the flexibility shown to families in Dublin at risk of losing their homes, with regard to increasing their rent supplement, to single persons and to other urban areas.

It also wants to see introduction of the new Housing Assistance Payment expedited, to replace rent supplement and legislation making it illegal for landlords to discriminate against rent supplement tenants.