Idina Menzel felt like a ''bad mom'' after the tooth fairy failed to visit her son.

The 47-year-old actress and singer revealed that her nine-year-old son Walker - who she has with former partner Taye Diggs - was devastated when he woke up after losing a tooth and found that the tooth fairy hadn't visited and left him money.

The Tony-winning actress wrote on Twitter: ''The tooth fairy didn't show up last night. Mom put tooth in tissue and son hid it under pillow.

''Then mom fell asleep and woke up this morning to son with tears. 'Tooth fairy didn't come'. That tooth fairy better get her s**t together. #badmoms (sic).''

Fellow actress Rachel Bay Jones responded: ''Been there. Look under the bed!''

The 'Frozen' star also received plenty messages of support from other parents, one of which compared Idina's experience as the tooth fairy to his as Elf on the Shelf - a Christmas game where a naughty elf magically moves around the house.

The user wrote: ''Sounds like the tooth fairy was as reliable as our Elf on a Shelf. Dude sat in the same place for like a week.''

The 'Rent' actress replied to the fan: ''Oh yeah that happened as well.''

Although Idina - who voices Princess Elsa in the animated film 'Frozen' - is well-loved by fans of the fantasy flick, she previously admitted that her new-found status as a role model hasn't been entirely easy to cope with.

She previously said: ''Everyone talks about me being a role model for young girls and that's not always the truth in my day-to-day personal life. I'm not constantly practicing what I preach. I'm a little uncomfortable carrying that banner. I'm not always 'Oh, I feel so great about myself today. I'm a powerful, confident woman, and I'm not going to care what anyone else thinks of me!' I mean it's all bull***t, really. I can be a mess. The older I get, I get wiser about some things, and yet I get more fragile and vulnerable about others.''