Len Evans, rep for Darlene tells TMZ ... Darlene won't be going after 'QOF' trademark, although its technically fair game, considering Mariah won't be able to own it either.

Len says, Darlene doesn't think one person should be able to legally own the title by trademarking it. Instead, the music legend feels the phrase should be free for everyone to use  ... considering there are a lot of folks who call themselves the Queen, and have had huge success in the holiday music genre.

What's more, she notes Mariah only has one hit Christmas song ... when there are folks with several holiday hits, who have not tried to get exclusive rights to the phrase.

For the record, Darlene's "Christmas (Baby Please Come Home)" is an absolute holiday banger, as are her versions of "White Christmas," "Winter Wonderland" and her 'Home Alone 2' track, "All Alone on Christmas."

As we've reported, MC's request to trademark the phrase was denied Tuesday by the U.S. Trademark Trial and Appeal Board.

Darlene was among others, like singer Elizabeth Chan, who were turned off when MC filed for the title back in March 2021 ... and it's fair to say she still disagrees with it now.

We're told Darlene also doesn't like the fact Mariah didn't acknowledge her comments about it ... and took it as a snub when MC responded to Dolly Parton's thoughts instead of hers.

Despite this, Darlene's rep says she has no beef with Mariah and would be happy to work with her fellow holiday queen.