Calls to devolve powers over flight taxes to Wales have been rejected by the UK government.
It follows a report by MPs in June, arguing Welsh ministers should control air passenger duty (APD) by 2021.
But UK ministers said on Friday they were concerned the powers could be used to promote Cardiff airport at the expense of Bristol airport.
Wales' Finance Minister Rebecca Evans attacked the decision as "totally unreasonable".
The Welsh Government has long argued for the powers, saying a tax cut could help Cardiff Airport, which it owns.
Passengers on economy class outbound flights of more than 2,000 miles pay air passenger duty of £78, with those on long-haul business class charged £172.
In a letter to MPs on the Welsh Affairs Committee, who conducted an inquiry an APD devolution, Treasury Minister Simon Clarke said it was not a question of not trusting the Welsh Government, but "previous statements from Welsh ministers have indicated that they consider control of APD as an opportunity to promote Cardiff Airport".
"This will naturally have an impact on Bristol Airport, Cardiff's closest competitor, and to a lesser extent other English airports.
"Evidence presented at the inquiry also made the case that consumers and businesses in parts of Wales, particularly in the north, are currently served by excellent connectivity at English airports.
"It is not clear how devolution in Wales would support these communities."
However, Mr Clarke said their aviation markets were "fundamentally different" and "the devolution settlements for the nations of the UK have always been asymmetrical, taking into account the specific circumstances for each nation".
The committee's chairman, Monmouth Conservative MP David Davies, accused UK ministers of offering a "flimsy excuse for why APD should not be devolved to Wales, despite it being devolved to Scotland and Northern Ireland".
He added: "I find the government's suggestion that it is 'not a question of trust', but rather of shared aviation markets, very unconvincing.
"I am disappointed that the government has not recognised the significant arguments my committee heard in favour of devolving APD to Wales and I know that many others will feel similarly."
Ms Evans said the UK government's decision "defies logic", adding: "Devolving APD would mean Wales would have the right to design a system that works for Wales - not the Westminster government.
"This decision does nothing to prove the prime minister's promise to unleash the productive power of the whole of the UK.
"We know there is unanimous support from across the aviation, tourism and business sectors in Wales for APD to be devolved and we will continue to press the UK government to change its position."