Stella Creasy, the MP for Walthamstow, said she was being harassed by anti-abortion group CBRUK because of her pro-choice stance.
The Advertising Standards Authority (ASA) said it had been “carefully assessing” more than 20 complaints.
Ms Creasy called on the Met Police to act to “stop the harassment”.
On social media, Ms Creasy also criticised both the Met Police’s refusal to intervene and Clear Channel, which owns the billboards.
The poster read: ‘Your MP is working hard… to make this a human right.’
Image: Twitter/ Stella Creasy
Now the MP wants companies to consider not buying from Clear Channel, after it sold a new advert showing a nine-week old fetus and a link to the website stopstella.com.
A Clear Channel spokesperson said: ‘We sincerely apologise for any offense that has been caused by a recent campaign which we ran in Walthamstow on behalf of a customer. We’re taking immediate action to remove this campaign.
‘As an Out-of-Home media owner, we take a neutral stance towards all advertising and have robust procedures in place to ensure that the creatives we run comply with the 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.’
In a tweet directed at the advertising company, Ms Creasy asked: ‘How much money did you take from (the Centre for Bio-Ethical Reform) to harass the women of Walthamstow? And why should any company ever advertise with you again given you are willing to put them alongside such hatred?’
Ms Creasy had previously labelled activists from the Centre ‘vile and awful people’, criticised the police response and urged supporters to donate to the charity Abortion Support Network.]
Having suggested the original image made her feel ‘physically sick’, the MP praised her constituents for their support, and shared an image showing one advert being defaced.
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 later shared by Ms Creasy shows that at least one of the six posters that have appeared around Walthamstow covered with white paint.
On its website, the Centre writes: ‘We are saturating Walthamstow, MP Stella Creasy’s constituency, with the humanity of the unborn child and the reality of abortion. Whilst highlighting to constituents how their MP is working hard to promote abortion as a “human right”.’ The group added that it was ‘holding multiple public education displays’, and ‘highlighting the humanity of the unborn child on billboards and advertising kiosks around Walthamstow.’
Image: Twitter/ Stella Creasy
Ms Creasy tabled a recent amendment to decriminalise abortion in Northern Ireland, which was passed by a majority in the Commons in July.
The MP’s office said she had also appealed to the Home Secretary Priti Patel to step in over the alleged harassment.
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.”