The Competition and Markets Authority has told the BBC it warned government officials that consumers could face risks from the fast-growing Covid PCR testing industry in April and May.
The business and competition regulator said it provided advice and market analysis to officials from the Department of Health and Social Care.
It said the advice detailed potential market and consumer risks.
It comes after the CMA was criticised by its former chairman this week.
Lord Tyrie told the BBC that the situation with PCR testing for travel was a 'predictable Covid rip-off', and that the competitions watchdog hadn't done enough.
The government has said it was provided with some general market analysis from the CMA on the potential implications for the PCR testing market and that its advice informed the government's approach on the private provider list.
The CMA said it cannot disclose this information.
The revelation comes after a summer of complaints from travellers and holidaymakers who have taken a holiday or visited family who they've been cut off from because of the pandemic.
The UK government has made it a condition of any international travel that tests before travel, and on your arrival in the UK are mandatory.
The number of tests that are needed is dependent on your arrival from either a green or amber country or your vaccination status. Arrivals from red countries must still use quarantine hotel facilities.
Some of the most common complaints from travellers mention tests listed on the government's list of providers that don't exist at the price advertised whilst others allege poor service.
At the start of August, the Health Secretary asked the competition watchdog to investigate "excessive" pricing and "exploitative practices" among PCR Covid test firms.
In a letter to the CMA, Sajid Javid said it was time for a "rapid high-level" review to protect consumers.
The BBC understands that a full CMA market study or investigation would require a formal consultation before an investigation could be launched and these investigations typically last between 6 and 18 months. Therefore, a wholesale reform of the market could be difficult because of time constraints.
It is understood that due to the time and process needed for a full review of the market, the Government was advised it is better placed to tackle immediate issues in this market.
The travel industry has been demanding action, after complaining about the 'onerous' level of testing in place, which they believe is a barrier to passenger revival.
But, given the lateness of any government intervention, and the impact on the travel sector, people in industry believe the damage has already been done.
Julie Lo Bue Said, chief executive of Advantage Travel Partnership, the UK's largest group of independent leisure & business travel agent experts, said "it feels like a PR exercise for the government to come out and say 'we're looking at this now'.
"It is far too late, when the public has had to pay for all these tests," she added.
On Friday, Sajid Javid, the Health Secretary announced that the price of PCR Covid tests provided by NHS Test & Trace for travel would fall, by £20 for one test to £68, and by £35 for two tests to £138.
The Government has consistently maintained that testing for travellers is in place to protect public health.