Almost three-quarters of undecided voters in eight Liberal party-held marginal seats say they disapprove of the federal government’s $4.6bn funding deal with the Catholic and independent school sectors, according to new polling data.

The ReachTel poll of 1,261 residents in marginal seats in Queensland, New South Wales and Victoria conducted on behalf of the Australian Education Union also found about half of undecided voters were less likely to vote for the Liberal party as a result of the deal.

The new data comes amid increasing tension between the commonwealth and states over education funding following the announcement of the private school deal.

It will give more ammunition to public school advocates including the AEU, which has promised to amplify its campaign for government school funding as the next federal election looms closer.

The poll was conducted on the evening of 27 September across the Liberal party-held marginal seats of Corangamite, Dunkley, Forde, Capricornia, Flynn, Gilmore, Robertson and Banks. It has a margin of error of between 3.4% and 3.8%.

Almost three-quarters (73.2%) of undecided voters polled said they disapproved of the funding deal, while 49.3% said they strongly disapproved.

The polling also found 52.9% of undecided voters and 38.6% of all voters said they were less likely to vote for the Liberal party as a result of the funding deal.

Of those who expressed a preference, Labor and Greens voters were most likely not to support the deal, although 21.3% of Liberal party voters polled across the eight seats also said they disapproved.

While polling across multiple seats can be an unreliable measure for individual locations, the result is likely to encourage pushback against the funding deal.

Already the federal education minister, Dan Tehan, is facing a revolt from state ministers who want increased funding for public schools as a result of the deal, while the AEU has promised to ramp up its Fair Funding campaign across 18 marginal seats.

Among those polled, 84% said education would be important in determining their vote at the upcoming federal election, with 53.7% of undecided voters saying education is “very important” in deciding who they will vote for.

Correna Haythorpe, the president of the AEU, said the poll showed voters had “not been fooled by the Morrison government’s cynical attempt to buy votes at the next election at the expense of students in our public schools”.

“Our ReachTel poll shows that prime minister Scott Morrison’s refusal to restore his funding cuts to public schools will have dire consequences for him and his government at the next federal election,” she said.

“Eight in 10 voters surveyed in our polling consider education a crucial factor in deciding who will get their vote.

“Prime minister Morrison may think he has settled the funding wars but voters are telling us that they don’t agree with him.”

Despite pushback from a number of state ministers, the commonwealth is seeking to reach a long-term education funding deal to secure the extra funding for the Catholic and independent sectors.

On Thursday Tehan told ABC radio he had spoken with all of the state and territory ministers “over the last few days” describing them as “very constructive”.

“They’ve been held in very good faith [and we will] continue to have them,” he said. “I’m confident we will get an agreement in the coming weeks and months.”