Fundamental changes are needed in the way business rates are calculated to make them fairer, says Angela Burns AM.
Speaking in a Welsh Conservative debate in the Senedd on business rates, Mrs Burns said that rates valuations need to be linked to turnover and not just rentable value.
A five-yearly revaluation has just taken place and in Narberth traders are facing, on average, a 160% rise in their bills. Some are looking at a 300 % increase. Businesses in Tenby are also facing massive hikes.
"If you are in the self-catering industry, or run hotels or pubs, then you are valued on your rent value, on the receipts that you take and on a number of other factors," she pointed out.
"But if you simply have a shop that sells toys or bits of material, then you are judged only on the rent of your shop. There is nothing else.
"So a shop could have a low turnover because it sells something quite specialised and the rent will be the same as the busy shop next door."
She also highlighted Narberth as a special case because more than half of the shops are owner occupied.
"So few premises are available for rent that it artificially drives up the costs," she added.
The Conservatives are pressing for responsibility for business rates to be transferred from the Social Justice and Local Government portfolio to Economy and Transport to ensure that the full economic effect of the business tax is properly evaluated.
Preseli Pembrokeshire AM Paul Davies said: "Business rates are the most significant fiscal leveller under the Welsh Assembly's control and are such an important economic tool it seems obvious that they should come under the Minister for the Economy."
Both of Pembrokeshire's Assembly Members are now pressing the Welsh Assembly Government to make an urgent announcement on the rates relief threshold.
"The Government is dragging its feet on this one and traders need urgent answers," said Mr Davies.
"In Northern Ireland they have postponed the revaluation altogether and in England they have raised the threshold in line with the general increase in revaluation.
"Yet in Wales we have no decisions yet, just a vague statement that they are "thinking about it." That is not good enough for the shops, pubs and hotels of Pembrokeshire who are going to go out of business while the Government drags its feet."
Mrs Burns has now written to every trader in Narberth to update them on her campaign against the rates increases.
"I have told the Minister for Local Government that a decision needs to be taken on raising the threshold as a matter of urgency and must be announced before Christmas," she said
