Some of the most influential political pollsters are ignoring millions of voters because they only call landlines. Even so, analysts are unsure whether that will affect the accuracy of the polling, despite one-in-five Australians being mobile phone-only users.

The number of people who use only mobiles grew by 20 per cent in the past year, to 3.3 million. Most users are city-dwelling renters, aged under 35.

A professor of politics at Macquarie University, Murray Goot, said that, while pollsters had been battling with the problem of changing technology for some time, there was no evidence that the mobile-only surge had affected the accuracy of the election polls.

”Landline response rates are almost certainly declining,” he said. ”As mobile phone use increases, pollsters will be increasingly concerned that they’re getting it right.”

But he said pollsters who did not call mobiles – Nielsen and Newspoll – ensured the spread of ages and gender matched those in the census.

Professor Goot said he was unsure if mobile-only users would vote differently to those using landlines.

”I think mobiles gradually will be called more, but it’s a question of how good the mobile databases are,” he said.

The number of mobile phones in Australia continues to rise, with the Australian Communications and Media Authority reporting there are now 24 million mobile phone services registered in Australia, compared with 10.4 million landlines.

The operations manager at polling company ReachTel, James Stewart, said acquiring mobile phone data lists could be expensive, and it  needed accurate address information to target seats.

ReachTel, which polls using a mix of mobiles and landlines, started contacting mobiles for polling purposes in 2011.

Essential Research, which uses online polling, has Labor at 50 per cent, on a level pegging with the Coalition on a two-party preferred basis.

Andrew Bunn, research director at Essential, said online polls were useful because they were cheap and accurate.

‘‘On average, the most accurate polls in the United States for [the] last presidential election were online,’’ Mr Bunn said.

Following the 2012 presidential election, statistician Nate Silver reported in The New York Times that ‘‘a number of polling firms that conducted their surveys online had strong results’’.

He said some telephone polls also ‘‘performed well’’ but those that only called ‘‘landlines… performed poorly and showed a more Republican-leaning electorate’’.

Newspoll chief Martin O’Shannessy said that, while mobile-only users ‘‘will be a problem one day’’, at this stage there were no issues with poll accuracy.

‘‘Telephone is still the only way to get to nearly everyone,’’ he said.

Nielsen polling director John Stirton said landline-only phone polls, conducted by trained interviewers, still continued to provide ”consistent and reliable results”.

Correction: This article has been amended to state the correct number of mobile-phone only users in Australia.

The original release of this article first appeared on the website of Hangzhou Night Net.