The number of people sleeping rough on Melbourne's streets has increased by 74 per cent compared to two years ago, a City of Melbourne survey shows.

The StreetCount survey involved 160 volunteers, who took to Melbourne's streets between 4:30am and 8:30am on June 7 to count the city's homeless.

The teams recorded 247 people sleeping rough on Melbourne's streets — a substantial increase on the 142 people recorded at the same time in 2014.

The volunteers found 184 people sleeping in parks, streets and squats and surveyed 63 people who slept rough at day centres.

Melbourne Lord Mayor Robert Doyle said it was worrying that the increase came at a time when the city was spending more on homeless services.

StreetCount survey findings: 195 men, 35 women sleeping rough; 17 could not be identified

195 men, 35 women sleeping rough; 17 could not be identified Most people aged between 26 and 60

Most people aged between 26 and 60 68 per cent of those surveyed had been homeless for more than a year Source: City of Melbourne

"That count has been consistent over many, many years, and now we've got a sudden jump — even with all the focus we've had in the last month on rough sleeping in particular," he told 774 ABC Melbourne.

"I think I'm going to have to look at some different short-term solutions, I'm going to have to work with Martin Foley, the Minister who is responsible."

Mr Doyle said causal factors of homelessness, such as mental illness and housing affordability, also needed to be looked at.

"We're going to have to look at those causal factors to see can we somehow interrupt this pattern that drives people into homelessness then doesn't provide a pathway out," he said.

Mayor 'not inclined' to empty building tax

Mr Doyle also said he would contact Vancouver Mayor Gregor Robertson, who is considering introducing an empty property tax to help ensure housing availability.

"I'm not inclined to that sort of a tax," he said.

"I don't think we've got the same problems Gregor has got, but, as I say, I'll contact him."

Launch Housing has called for a similar measure, saying it would make housing more affordable.

Councillor Richard Foster said the StreetCount research helped the city plan and develop its homelessness strategy.

"The StreetCount data provides a better understanding of the needs of people sleeping rough in Melbourne, allowing us to plan, develop and make decisions about long term solutions to homelessness," he said.