Auckland's rental crisis is worsening, with prices rising 7 per cent in a year and desperate tenants going to extreme measures including offering to pay six months' rent in advance.

New figures show rents in the most desirable suburbs have jumped an extraordinary 24 per cent.

A lack of new construction and increasing demand from a booming population unable to get on to the property ladder are among factors getting the blame.

Last week, the Herald reported how 200 would-be tenants looked through one Kingsland rental property in just 30 minutes.

Real Estate Institute chief Helen O'Sullivan yesterday blamed the rental shortage on "pure demand and supply".

She said very little building had been done in the past 18 months as developers struggled to find finance for developments that were traditionally sought after by first-home buyers or people looking for investment units.

"You look around Auckland and you're not seeing major housing developments in rental pockets under way anywhere. The supply hasn't increased and demand has indeed grown," Mrs O'Sullivan said.

Nationally, rental prices have risen 3 per cent, according to Crockers Property figures released yesterday.

But in Auckland, the rise is more than double that.

It has been driven by rental prices in the desirable city-fringe areas such as Grey Lynn and Westmere where median rents for a three-bedroom house reached $675 a week in January - an increase of 22 per cent on the same time last year.

The median price for a three-bedroom house in Epsom, Newmarket and Royal Oak increased 24 per cent to $585 a week.

However, the soaring rents are doing little to deter would-be tenants who are increasingly desperate to find a place to live.

Harcourts Ponsonby property manager Sharon Ryan said it was not unusual for applicants to offer more than the advertised rental price for homes in Ponsonby, Herne Bay, Freemans Bay and Parnell.

She said some tenants were even signing tenancy agreements without viewing the property first - and in one case someone offered to pay a six-month block of rent up-front.

"You always get a bit worried when they haven't seen it. I always say it is better to look first, but I had a girl who had missed out on quite a few properties before and she already knew the complex," said Mrs Ryan.

Other tenants were willing to pay double rent - shelling out for a new property while still paying rent on their current place - to ensure they did not miss out while they gave the required three weeks' notice.

"Sometimes it is really hard to decide, because you will get six applicants and they are all good. Sometimes what it comes down to is first in/first served," said Mrs Ryan.

Yesterday, an open home for a three-bedroom townhouse in Grey Lynn advertised at $680 a week - $5 above the average price - attracted 12 people in half an hour over a mid-week lunch time.

Barfoot & Thompson property manager Maureen Kan said the shortage meant landlords had started to ask for more rent.

But she warned that even in a tough market, a property could sit vacant for the sake of $20 or $30 more a week.

"Basically the market is the market. Tenants know what is out there and they have seen enough properties to know when something is overpriced," said Mrs Kan.

In some areas of Auckland, however, there has been a slight drop in the median rental price.

In Devonport and Takapuna, rents were down 4 per cent last month when compared to the previous January.

Geri Martin, of Bayleys in Takapuna, said it seemed landlords in the area were trying to cater to "fussy tenants".

"Tenants are really fussy - if they don't like something in the house they won't pay as much, or won't rent."