The commission made the remark during discussions with related agencies to follow up on the merger deal between telecom giants True Corporation and Total Access Communication (DTAC).
Commission adviser Kanapol Tuisuwan said the merger deal worth 217 billion baht is considered the biggest deal in Thailand.
If the merger deal is completed, True and DTAC will be able to generate 83 billion baht in annual revenue, impacting the country's gross domestic product, he added.
He also pointed out that the merger deal would lead to market domination, adding that the government will lose benefits during the new round of spectrum concession auction.
He further added that True would gain 1.58 billion baht in profit from the merger deal.
However, an NBTC representative stated that the watchdog has the authority to prevent market domination by an entity.
The representative also asked for more time to consider the deal, but the consumer protection commission noted that a delay by the NBTC would be a dereliction of duty, as there has been no answer to society until now.
The commission also believes that the NBTC's move would lead to mergers without measures to protect consumers' interests.
Meanwhile, a representative from National Telecom (NT) said it is the NBTC's duty to consider the merger deal.
It pointed out that the merger deal would cause an impact on market share in the telecom industry. The market share of True and DTAC would jump to 54 per cent compared to 46 per cent of another telecom giant Advanced Info Service (AIS).
The market share of True and DTAC is currently 32 per cent and 22 per cent, respectively, the NT representative said.
It said the merger deal would force small telecom operators and mobile virtual network operators to close their business.
The NT representative also predicted that the merger deal would impact consumers' alternatives and service efficiency.
It added that service fee would increase and there would be no need to launch promotional campaigns.