Almost 40 per cent of voters who would otherwise support the Berejiklian government would be less willing to because of its Sydney stadiums policy, a survey shows.

The $2.5 billion plan for two new stadiums announced by Premier Gladys Berejiklian and Sports Minister Stuart Ayres in November has become a running sore for the government, amid a consistent refusal to release analysis supporting the plan, and backbench unrest.

NSW Premier Gladys Berejiklian told Fairfax Media in 2017 that "governments don't always get everything right and sometimes we have to acknowledge that."

The survey result comes as documents obtained by the Herald show the SCG Trust's push for more funding for Allianz Stadium began just days after former premier Mike Baird ruled out paying to build a new stadium in Sydney's east.

Multiple opinion polls have suggested the policy – which appeases the influential Sydney Cricket & Sports Ground Trust by committing to build a new stadium at Moore Park – is deeply unpopular.

And a new analysis suggests the policy’s unpopularity is extending across party lines.

The analysis by Micromex Research and Consulting, a company that conducts surveys for local councils and state government agencies, shows 37 per cent of respondents who identified as supporting the Coalition would be less willing to vote for Ms Berejiklian’s government if it followed through on plans to build new stadiums at Moore Park and Olympic Park.

A December survey conducted by Micromex found 67 per cent of overall respondents were opposed to Ms Berejiklian’s stadium policy, while a Herald commissioned poll last week showed almost 60 per cent of voters were opposed to the plan. The Herald poll did, however, show an increase in the Coalition's primary vote from 37.6 per cent in October to 41.9 per cent.

Allianz Stadium and Premier Gladys Berejiklian. AAP

One main difference between Ms Berejiklian’s $2.5 billion stadium plan and the $1.6 billion plan of her predecessor, Mike Baird, was Mr Baird’s decision to disappoint the SCG Trust and not build a new stadium to replace Allianz Stadium at Moore Park.

Ms Berejiklian, however, has accepted the advice of the SCG Trust that the 30-year-old Allianz Stadium is in dire shape and would be best replaced by a brand new facility.

The Herald has obtained documents detailing the SCG Trust’s efforts to obtain funding for a replacement stadium at Allianz in the months following Mr Baird’s announcement in April 2016 that he would not fund a new stadium in Sydney’s east.

Less than a month after Mr Baird said his government would not build a new stadium at Moore Park, the SCG Trust had sent two letters to the NSW Office of Sport about safety, security and compliance issues at Allianz Stadium, according to a chronology compiled by lawyers for the SCG Trust obtained using freedom of information laws.

The correspondence from the Trust - whose trustees include influential broadcaster Alan Jones, businessmen Tony Shepherd and Maurice Newman, and former News Ltd boss John Hartigan - intensified during mid-late 2016 and early 2017, as it commissioned multiple safety and security reports that identified problems with the stadium.

In that time, the estimated cost of repairs to the existing stadium continued to increase. Analysis commissioned by the Trust in 2014/15 showed safety, security and compliance works on the existing stadium would cost $128.15 million (in 2015 dollars). But by late 2017, a KPMG analysis put the cost of repairs to Allianz Stadium at $500 million.

It was on this basis that the Berejiklian government committed to building a new stadium for around $705 million.

But the government has not released the KPMG analysis, nor separate analysis that purports to show it would not be economic to simply refurbish ANZ Stadium at Olympic Park, rather than build an entirely new stadium.

Stu Reeve, the managing director of Micromex, said he conducted the survey in the past week to gauge whether attitudes to the stadium plan had changed.

“It still does not resonate,” said Mr Reeve.

After first asking how likely respondents were to vote for the Coalition government, the survey asked whether, should the government proceed with building two new stadiums, respondents would be likely to change their vote.

Among all respondents, 51 per cent said the stadium policy would make them less likely to vote for the government.

Contacted about the survey, Mr Ayres said: “We need to make tough political decisions to make sure we keep the thousands of jobs and tourism dollars that comes with securing major events.

“There is no change to the NSW government’s stadium policy announced in November last year.”

Micromex was not commissioned to conduct the recent survey.

Correction: An earlier version of this story incorrectly cited the Liberals' primary vote as the Coalition's primary vote.