Environment Canterbury are counting on an influx of workers into Christchurch's CBD to jump start the number of bus users.

Patronage is down 3.5 percent in Christchurch since July.

Environment Canterbury thinks cheaper prices at the petrol pumps is to blame for a fall in bus users.

ECan public transport manager David Stenhouse said it is a theme across most of the country.

"There's only one region that is showing growth in public transport and that is Auckland whereas the rest of the regions have seen significant patronage decline, or at least it's fairly stable and there's no growth, that's largely a result of lower fuel prices."

But the number of people using the high frequency purple and orange lines did see increases, around 10 percent.

Mr Stenhouse said they expect that to spread as more workplaces move back into the CBD.

"It's something like 50,000 employees that will be back into the city by 2021, but this is a big influx over the next 12 to 18 months, so yes we would expect that growth to continue."