In a flurry of messages, she defended women who have abortions because she said she was sick of seeing families break up after having children.
But later on, she claimed the Tweets were actually lyrics from an upcoming album track, asking her followers: "Excited?"
The 27-year-old, who gave birth to daughter Ethel last year and is expecting her second child with builder husband Sam Cooper, waded into an abortion row after Health Secretary Jeremy Hunt said he would like to see a ban on terminations more than 12 weeks into a pregnancy.
Lily, who has suffered two miscarriages, tweeted:
Can small minded idiot blokes stop telling women whether or not they're entitled to abortions please? #enoughnow
The star, who was raised by her mother Alison Owen after her famous actor father Keith Allen left the family, added: "Babies are lovely but quite hard work ... Sometimes there are lovely dads who take their responsibilities very seriously and work very hard to look after their babies. These men should be applauded.
"But sometimes, quite often, when the baby cries a lot the man gets frustrated and leaves the baby and the lady that had the baby. Lily wrote: "He sticks his fingers in his ears and pretends that the baby isn't really there, he stops answering his phone when the lady calls.
"The lady gets very sad and feels very alone and angry and even though she loves her baby more than anything ..."
"She wonders what her life might have been like if she had never had the baby in the first place ... So to all the Pro Lifers spamming me with s***.
She added: "This is one of the many reasons I believe a woman should have a right to choose.
The day the number of single father households equal the number of single mother households is the day I start to listen to their views.
She later claimed the messages were lyrics from an upcoming track, telling fans: "Those were the lyrics from the first single, excited?"
Lily's messages received a huge backlash from pro life advocates and men being horrible about women – prompting her to tweet:
Wow there are ALOT of women haters out here. Scary s***.#myuterusisMYuterus.