OFFICIAL government figures on the state of Victoria's rental market have been missing since May and, when they finally are released, are likely to be nine months out of date.

Substandard data collection has been blamed for the long delay in the Office of Housing's quarterly rental report, which last published figures from March.

The Residential Tenancies Bond Authority, a government agency under the auspices of Consumer Affairs Victoria, is responsible for collecting the information and outsourced the task to an Indian-based company, iGate, which has offices in Ballarat.

The data was then passed on to the Office of Housing for analysis but was said to be unusable.

"I was not prepared to publish data that we could not stand by," Housing Minister Richard Wynne said.

The information in the Rental Report is considered a truer indication of the state of the market because the authority records all official rental agreements lodged in the state.

Figures provided by the real estate industry rely on publicly advertised rent or rents reported by agents.

Reports of Melbourne's rental vacancy rate have swung from a tight 1.2 per cent to a healthier 3.9 per cent.

The Office of Housing's December quarter figures are now expected to be published on time in March, while the figures from June and September 2008 will be rolled into one report.

But Opposition Housing spokeswoman Wendy Lovell questioned the delay and said Victorians had been left in the dark about the market.

"You've got to wonder what they are trying to hide." she said.

The Tenants Union of Victoria's Toby Archer said accurate and up-to-date information was "crucial" as the state's rental crisis continued.

A spokeswoman for Consumer Affairs Victoria said data collection for the report had always been outsourced but iGate had been contracted only since July.

"As sometimes happens when moving to a new processing system, a number of teething problems occurred," she said. "These issues have since been resolved."