Global oil prices have been declining for several weeks, but a price war between Saudi Arabia and Russia has seen a dramatic plunge in the past 24 hours.

Last month, the RACT estimated the gap between wholesale and retail prices was 25 cents, which it claims has increased to 30 cents this week.

Read more: The 2016 ACCC report into Launceston's fuel prices

RACT general manager of mobility services Darren Moody said retailers were failing to pass on the dropping fuel price.

"We've been expecting there will be a substantial decrease to the retail price for some time, however we're seeing almost nothing," he said.

"Today's terminal gate price is 125.3 cents - on that basis, prices should be less than 140 cents and ideally about 138.

"This over-charging has been ongoing for two to three weeks."

On Tuesday afternoon, most Launceston petrol stations were displaying unleaded prices of 156.9 cents.

The Australian Competition and Consumer Commission completed a report into Launceston's petrol market in 2016, finding a lack of competition and no transparency in pricing was harming consumers.

The RACT has been calling for a fuel watch-style system to operate in Tasmania, like in NSW, however this has not occurred.

Economists have predicted mainland fuel prices could drop to $1 a litre, however Mr Moody said this was highly unlikely in Tasmania.

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"I'm of a view that Tasmania's won't see $1 a litre," he said.

"I'm also of a view that the current stoush between OPEC and the Russians will resolve itself in the next few weeks.

"The low prices will be around for a while. At the moment, they're in full production so they're creating a whole bunch of stock, and then that stock will take a while to run through."

Despite having a commercial partnership with United Petroleum, Mr Moody said the RACT "did not have any direct control over their prices".

"We have, and will, continue to talk to United about their prices," he said.