The singer, 29, was replying comments made by outspoken Katie, 38, in her column for The Sun.

Speaking of a video Lily recently posted to Instagram of herself, Katie said she was a “short a*se mother in big pants”.

Lily hit back at Katie on Twitter, after a magazine posted an article which featured Katie’s comment about her.

She wrote: “@OK_Magazine @KTHopkins honestly defines unnecessary, as does this article, as does this magazine.

“Fat shaming, woman hating, moral high ground f***tards. Just stop your pathetic existence, you do nothing…….for anyone srlsy”

But Katie’s comments had obviously upset Lily, who then posted: “@KTHopkins tipping off the paps that you’ll be f****** someone in a field = unnecessary, also deluded and self important, #begone.”

Never one to shy away from an online argument, Katie responded to Lily’s tweets. She wrote: “I may have dined al fresco, but at least I didn’t film myself doing it & I had someone else to hold my arse in for me.”

Lily replied: “@KTHopkins sure, I bet those paps were just hanging out in some suburban field and just happened to stumble across your ‘romp’”.

Apprentice star and mum-of-three Katie then got Lily’s children involved, saying: “Field or no field, at least I have someone to hold my boobs in for me @lilyallen PS your kids asked who was in this photo”, before posting a picture of Lily holding her boobs.

This is not the first time Lily and Katie have clashed on Twitter. Katie cruelly said that pregnancy for mum-of-two Lily involved ‘gaining two stone and looking pretty hideous.”

At the time, Lily said: “Fat shaming, you were a stone out, I gained 3 not 2. And hey, look I’m on the cover of Elle this month !”