UPDATE: WET conditions unsuitable for planned burn-offs are the reason Victoria fell short off its target, the state government says.

A document leaked to The Age newspaper has revealed the government achieved only 16 per cent of its target in the densely populated central region, which includes 54 towns in areas such as the Dandenongs and Yarra Ranges.

But the Department of Sustainability and Environment reached 150 per cent of its goal in the less populated northeast, where 20 towns are at extreme bushfire risk.

Environment Minister Ryan Smith said most of the state was flooded last January and areas such as the Yarra Ranges and the Dandenongs had significant rainfall late last year.

"You just simply can't burn where it's wet," he told reporters in Melbourne.

Mr Smith said large-scale burning had to be done in less populated areas.

"Much of the ember attack that we saw during the bushfires a few years ago came from several kilometres back from the front," he said.

"It's by burning those big, broad-scale areas that we are able to protect homes."

Mr Smith said burning targets were rolling and any shortfall due to weather conditions would be added onto the next period.

DSE chief fire officer Ewan Waller said that 94 per cent of the burn target was achieved during one of the state's wettest years on record.

He said more than 30,000ha were burnt last spring, more than ever before.