The regulator told the BBC it provided advice and market analysis to officials from the Department of Health and Social Care in April and May this year.
According to reports, advice detailed "potential market and consumer risks".
It comes after the former chair of the CMA, Lord Tyrie, slammed the watchdog for being "too slow to react" to complaints about testing providers, describing the situation as a "predictable Covid rip-off".
The government told the BBC it was provided with "some general market analysis" from the CMA on the potential implications for the PCR testing market and the advice informed the government’s approach on the private provider list.
The CMA reportedly said it cannot disclose this information.
