Motorists are being hit by the ''dirty two'' of fuel pricing - a lower dollar and higher wholesale prices, says the RACT.
Many Launceston petrol stations are advertising fuel at 158.9 cents a litre, a 10 cent increase in a few weeks.
RACT spokesman Vince Taskunas yesterday said the price of refined petrol and diesel in Singapore, a major source of Australian imports, increased sharply at the end of January and the start of this month.
Also, the Australian-US dollar exchange rate dipped.
As fuel is priced in US dollars, this made fuel even more expensive.
He said Hobart prices went up earlier, as the sales volume was larger so stock turnover was quicker, but the entire state was at a disadvantage compared with other areas.
Mr Taskunas said the trend of Tasmanian petrol and diesel prices was virtually a constant upward slope, with the occasional plateau.
He said in other states, prices sometimes went down when wholesale prices dropped but for some reason this rarely happened in Tasmania.
''These (latest) price increases are pretty serious,'' he said.
''That is $5 for an average tank fill.''