In a decision that has prompted accusations of an election year cover-up, Ambulance Victoria has refused to publish response times to cardiac arrests by local government area because it might "inflame" its industrial dispute with the paramedics' union, discourage Victorians from ambulance membership, and make people drive themselves and others to hospitals instead of calling 000.

In July, the paramedics' union, Ambulance Employees Australia, applied under freedom of information for response times to cardiac arrests by local government area over a five-year period.

But earlier this month, Ambulance Victoria said such data was exempt under Section 34 (4) of the Freedom of Information Act 1982, which says an agency engaged in trade or commerce does not have to publish information that is of "a business, commercial or financial nature", which if disclosed would likely expose the agency to "unreasonable disadvantage".

It also said that there was potential for the data to be confusing because it did not include cases attended to by firefighters and volunteers and would include cardiac arrests witnessed by a paramedic when they had arrived at a scene, as oppose to cardiac arrests that precipitated a call for help. Ambulance Victoria said the former are excluded from performance targets.

Furthermore, it said any public interest in transparency and disclosure was already met by publication of less specific data on response times.

"There is clear potential for confusion, misunderstanding or unnecessary debate with respect to response times to cardiac patients. There is also a clear public interest in maintaining public confidence in the delivery of ambulance services, confining the current industrial action and increasing subscriptions for ambulance services," Ambulance Victoria said.

The state opposition was denied similar data by the Victorian Civil and Administrative Tribunal, which ruled in favour of Ambulance Victoria.The VCAT decision said the data might put Ambulance Victoria at a disadvantage by discouraging ambulance membership and encouraging people to drive themselves to hospital.

Both decisions have occurred despite a 2010 recommendation from the Victorian Auditor-General that Ambulance Victoria "publicly reports a comprehensive suite of response time indicators, including ... a breakdown of performance by region/locality".

Union secretary Steve McGhie, who has been trying to get the government to provide paramedics with better conditions since August 2012, accused the government of instructing Ambulance Victoria to hide the figures because it had failed its previous election promise to improve the service. He said rising demand for the service and increasing queues at busy hospitals meant paramedics were finding it increasingly difficult to get to new patients fast enough.

"This is about the performance of an emergency essential service. I would have thought Victorians are entitled to debate its performance... particularly when it is paid for by taxpayers' money," he said.

Opposition health spokesman Gavin Jennings said: "With less than 70 days to go before the election, the Napthine government is trying to prevent the public from finding out just how bad the ambulance service has become."

Ambulance Victoria CEO Greg Sassella did not respond to questions about a cover-up but said the decision was open to appeal. A spokesman for Health Minister David Davis said data reporting should not be done for smaller areas because of the way the state-wide system worked.