An anti-abortion billboard campaign targeted at pregnant MP Stella Creasy is being pulled down amid claims the posters were a form of harassment.
The Walthamstow MP said she was being targeted by anti-abortion group CBRUK because of her pro-life stance.
Clear Chanel, which owned the billboards, apologised and said it was taking immediate action to remove them.
Ms Creasy has called for the company to donate money from the campaign to an abortion support charity.
Earlier on social media, she criticised the Met Police’s refusal to intervene and to act to “stop the harassment”.
The ASA said it had so far received 20 complaints about the poster campaign.
“Our rules state that ads must not contain anything that is likely to cause serious or widespread offence,” an ASA spokesperson said.
In a statement, Clear Channel said it took a “neutral stance” on advertising and had processes to ensure all posters complied with UK Advertising Codes.
“While this campaign met these requirements, we accept that the content should have been scrutinised in greater detail and should not have been displayed,” it said, adding that it would review its internal processes to ensure it did not happen again.
Ruth Rawlins, of CBRUK, claimed Ms Creasy had shown “hypocrisy” by only using the word baby “when a child is wanted but totally ignores the word in conversations about an unwanted baby”.
She added: “We will, in the near future, be holding other MPs to account.”
At the weekend the anti-abortion group, which is affiliated to the CBR group in the United States, leafleted shoppers in Walthamstow High Street. The Met said officers had attended the planned protest, which “concluded peacefully”.
“Officers listened to concerns about the content of parts of the protest but no criminal offences were committed,” the force said in a statement.
A picture shared by Ms Creasy on Monday showed one of the six posters that appeared around Walthamstow had been covered with white paint.
The MP’s office said she had also appealed to the Home Secretary Priti Patel to step in over the alleged harassment.
Ms Creasy tabled a recent amendment to decriminalise abortion in Northern Ireland, which was passed by a majority in the Commons in July.
Ilford Labour MP Wes Streeting on Twitter described the poster campaign as “appalling”.
“Just so we’re clear about what’s happening here, protesters have made it clear that they are targeting Stella while she is pregnant because she is pregnant.”
Comedian Shappi Khorsandi added her voice to the objections and said: “‘Stop Stella’????. This isn’t free speech, it’s harassment.”