Faster broadband, internet television services and better retail offers are driving a switch to uncapped broadband plans.

A third of internet users have ditched data caps and switched to broadband plans that allow unlimited downloads, according to a Statistics NZ survey.

The department said internet users were consuming more than twice as much data as two years ago, with average monthly consumption jumping 143 per cent to 45 gigabytes per household in June.

Statistics NZ senior manager Jason Attewell said the increase had in part been driven by the uptake of recently-introduced internet television services such as Lightbox, Neon and Netflix.

The proportion of people using uncapped internet plans had quadrupled since last year, the survey found.

John Butt, chief executive of Wellington-based internet testing firm Truenet, said internet providers appeared to have got on top of the problems that emerged in March and April when increased traffic had led to congestion and a drop in internet speeds at peak times.

That congestion, which had peaked during the early evening, was now "tapering off", he said. In particular, Truenet had detected a "phenomenal" improvement in Vodafone's cable networks in Wellington and Christchurch since it completed a multimillion-dollar network upgrade on September 30, he said.

About 5 per cent of broadband connections were now provided over fibre-optic cable and the number of people using ultrafast broadband was growing "exponentially", Statistics NZ said.

Exploding demand for broadband data is not necessary positive for telecommunications companies.

Analyst J P Morgan said many Asian countries were likely to have to nationalise or otherwise centralise the control of their telecommunications networks to ensure sufficient investment to keep up with demand. It forecast the profitability of networks in countries such as India and the Philippines would drop significantly.

Scott Puopolo, an executive with United States network equipment vendor Cisco, is currently in New Zealand.

He is advising telecommunications firms that the current model of "integrated telecommunications businesses" is broken, and that despite growing network traffic volumes, revenues are flat and the profitability of the industry is falling.