Symantec was "nervous" of the effect Microsoft Security Essentials would have on the threat landscape, claiming the product does not provide adequate protection and would lull consumers into a false sense of security.
Mike Plante, senior director at Symantec, attacked Microsoft for "putting consumers at risk because [Microsoft Security Essentials] doesn't block a lot of the malware attacks that these criminals are throwing at consumers".
He said Symantec was "nervous" the product would be used by consumers who are not savvy enough to realise its failings.
"Based on what we have seen from AV Comparatives and AV Tests, Microsoft's anti malware engine, at the time called OneCare, does not measure up to the other freeware players, let alone the players like Norton," Plante said.
Microsoft denied its product, which was launched yesterday, was inadequate.
Its chief security advisor for Australia Stuart Strathdee said he wasn't interested in "trading blows with our competition" and instead explained that Microsoft Security Essentials was based on its Forefront enterprise product, which he believes is sound.
"We want to expand the level of protection and expand the overall volume of consumers who are running security software. This application is basically running the same engine as our Microsoft Forefront product. We stand by that product," Strathdee told iTnews.
According to Strathdee, the product does not require any more functionality - such as heuristics - as long as users keep their operating system and applications up to date.
"The overall strategy here is very clearly, Windows 7 with IE 8 and Microsoft Security Essentials.
"It is not only just about whether the product does heuristics or if it has other functionality built into the AV product. It really is a strategy about making sure you have the latest operating system, the latest browser and some anti malware and anti virus protection built in.
"Windows Vista and Windows 7 also have Windows Defender built in. When you combine that with the security features built into IE8 you can see the overall strategy of defence in depth coming into play," added Strathdee.
Symantec's Plante dismissed any threat Microsoft Security Essentials may have on Symantec's market share.
"This market is crowded already and Microsoft is really just joining that fray. The early reviews of the product aren't that good and as a free solution [Microsoft] will be somewhat restricted in the marketing they will put behind it. I don't think this is going to change the dynamics," added Plante.
In a report published by Gartner in June, research analysts Arabella Hallawell and Neil MacDonald said Microsoft had an opportunity to alter the consumer security market but suggested the company's investment in the product would be considered a failure if it did not capture at least 20 percent of the market within two years.