Michelle Williams is insecure about her singing abilities because she was once told she had the least "commercially appealing voice" in Destiny's Child.

The 40-year-old singer opened up about her struggles during an interview with Billboard.com, after being unveiled as The Butterfly on U.S. TV show The Masked Singer on Wednesday night.

Asked if it was true what she'd said in her VT about being insecure about her voice, Michelle replied: "That was no lie. Because I've done a lot of gospel, so I'm kind of insecure because mainstream (fans) don't know my voice. And sometimes social media... it's bad when you read the comments. I like engaging with people on social media. I don't want to not talk to the people that are being gracious all because there are some mean ones out there.

"But sometimes before you get to the nice ones you have to get through a couple mean ones. Apparently, I don't have the most commercially appealing voice or whatever. People have their favourites, but vocally I was not a favourite in the group, and that stuck with me."

Michelle had to keep her involvement in The Masked Singer a strict secret from her nearest and dearest, including former Destiny's Child bandmates Beyonce and Kelly Rowland.

But while she was determined to abide by the rules of the non-disclosure agreement she signed to keep her role on the programme a secret, that didn't stop her pals figuring out it was her on the show.

"I've been getting text messages from Bey, Kelly, my cousin - so I know people are watching," she laughed. "But I don't want to say nothing. But I'm gonna go ahead on and say it: Bey and Kelly know it's me. They know my voice. They know! They know it's me."