Megan Fox has hit back at an online troll who criticised her parenting.

The 36-year-old 'Transformers' star saw red after she was mum-shamed on Instagram by a follower who left a mean-spirited comment on her sexy pictures asking the actress "Where your kids at?” - prompting a fiery response from Megan who replied with a sarcastic message.

In a screenshot obtained by E! News, Megan was seen to have posted: "Wait wait wait. I ... have kids?!? ... Oh my God I knew I forgot something!! Quick, someone call the valet at the Beverly Hills hotel. That’s the last place I remember seeing them. Maybe someone turned them into lost and found."

Megan is mum to three children - Noah, 10, Bodhi, eight, and Journey, six, with her ex-husband Brian Austin Green and she recently opened up about how she struggles to cope with being away from them when she's travelling for work.

In an interview with Glamour magazine, Megan revealed she often breaks down and cries when she's separated from her boys.

She said: "It is hard, because I travel for long periods of time and they have to attend school, which is what it is. I wish I could take them out to travel with me, it would make things a lot easier.

"I get in the bath and cry a lot about it because it is hard and not because of pressures that anybody else or society puts on you, but it is just hard being separated from them in that way. They are my DNA."