Fuel was given away for free today at Fyshwick, causing a scramble among Canberra's cost-conscious motorists.

Between 12:00pm and 2:00pm, E10 unleaded petrol and diesel at Metro Petroleum on Barrier Street were listed at 0 cents per litre, with regular unleaded signposted at 2.7 cents.

The drastic price drop was not a glitch in the petrol station's electronic signage, but a promotional special to coincide with the launch of a new app.

Each motorist was restricted to a limit of 50 litres.

The petrol station said earlier this month it would be selling petrol at 9 cents per litre today, but dropped the cost to nil at the last moment.

The first arrival waited almost two hours to fill up his tank and he was not alone.

More than 100 motorists keen for a bargain in Canberra's expensive fuel market were quick to take up the offer, queuing all the way down Barrier Street despite heavy rain.

Traffic management was in place around Barrier Street but cars were able to pass through.

Canberra petrol prices remain 'unusually high'

Despite the drop at Fyshwick, prices remained high elsewhere in the territory.

Last week's unleaded average was 125.9 cents, despite the fact that elsewhere in Australia prices dropped below $1.

For two hours diesel and E10 fuel were given away for free. ( ABC News: James Fettes )

NRMA director Kate Lundy welcomed the special, and said it put a spotlight on the high cost of petrol in Canberra.

"Sure it's a stunt, but it's a stunt that's highlighting the fact that we're still paying too much for petrol," she said.

"ACT motorists are pretty fed up with unusually high petrol prices relative to other markets in the eastern states in Australia.

"We know that the ACT market is dominated by the big supermarkets, Coles and Woolies.

"That contributes to us paying a higher price than we ought to if you look at our pricing relative to places like Sydney."

Chief Minister Andrew Barr called on the competition watchdog to investigate.

"I have written to the Australian Competition and Consumer Commission (ACCC) asking that one of their deep dives on competition in petrol retailing … that they look at Canberra," Mr Barr said.

"They haven't done that today, but I'm hopeful that they will as part of a future round of investigations."

Ms Lundy said while the ACCC had been keeping an eye on the Canberra market, continuing high prices showed more scrutiny was needed.

"The ACCC has a program of monitoring, clearly it's not strong enough," Ms Lundy said.