An advertising agency has apologised for running a campaign against the Labour MP Stella Creasy by an anti-abortion group, which included a billboard featuring a foetus and the words “Stop Stella”.

The company, Clear Channel, said it would like to “sincerely apologise” for any offence caused after the poster appeared in Walthamstow, north-east London. “We’re taking immediate action to remove this campaign,” a spokesperson said.

Creasy, who represents Walthamstow in parliament, is the subject of a targeted movement against her that calls itself “Stop Stella”. The protest and campaign was set up by the UK branch of the American anti-abortion organisation the Centre for Bio-Ethical Reform.

It comes after MPs approved an amendment by Creasy to extend abortion rights to Northern Ireland, the only part of the UK where it remains illegal. The vote was passed by 332 to 99.

On Monday, someone covered the advert in her constituency with white paint. Creasy tweeted to say: “I would rather @CCUK_Direct took this advert down, the @metpoliceuk acted to stop the harassment and @patel4witham brought in buffer zone legislation to deal with these people in first place – but in the meantime [it] seems Walthamstow has my back.”

stellacreasy (@stellacreasy) I would rather @CCUK_Direct took this advert down, the @metpoliceuk acted to stop the harassment and @patel4witham brought in buffer zone legislation to deal with these people in first place - but in the mean time seems Walthamstow has my back ..#lovewalthamstow #hatebullies pic.twitter.com/gRwrEG8jv1

A spokesperson from Clear Channel said: “We sincerely apologise for any offence 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.”

The agency said it took a neutral stance towards all advertising and had robust procedures in place to ensure that the content it runs complies 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,” the spokesperson said.

The company added that they were reviewing the internal processes in place regarding the campaigns and content they run.

It comes after protesters entered her constituency on Saturday and put up a poster of her next to a picture of what it claimed was “a 24-week-old aborted baby girl”. The image read: “Your MP is working hard … to make this a human right.” It also featured the address of a website set up against the MP.

A number of public figures have come out in support of Creasy, including the TV presenter Kirstie Allsopp. She said of Clear Channel Direct, the agency that was paid for the adverts: “Taking money for ads of that kind aimed at @stellacreasy and women in Walthamstow is appalling. No decent firm should spend money with you.”

Sarah Champion, the Labour MP for Rotherham, tweeted: “Dear God this is sick! The fact an ad company is making money from this harassment of a pregnant MP is as bad as the campaign group.”

The leader of Waltham Forest council, Clare Coghill, said: “I defend anyone’s right to lawfully protest but when it changes into the targeting of individuals in such a personal way, we must come together to say this isn’t acceptable.”

She said that the council were looking at all the powers it has at its disposal to ensure the safety and wellbeing of the local MP and the wider public. She added that a complaint had been made to the Advertising Standards Authority around the billboard’s content.

The Metropolitan police said they attended the protest on Saturday but there were no offences and no arrests took place. They said they did not receive any complaints about the contents of leaflets or posters at the event.

Creasy said she was being targeted because she was pregnant, with people accusing her of being a hypocrite.

The website set up by the Centre for Bio-Ethical Reform against the MP includes a section that reads: “Stella Creasy deliberately conceals in all her public statements and dialogue on abortion … the humanity of the unborn child and what an abortion procedure actually entails.”

It added: “Yet when she is speaking about her own baby in her womb, and her previous miscarriages, she speaks openly on their humanity.”

Creasy’s amendment argued that abortion laws in Northern Ireland, where women seeking terminations could face life imprisonment, were contrary to international human rights norms.

“How much longer are the women of Northern Ireland expected to wait?” she told MPs. “How much more are they expected to suffer before we speak up … as human rights defenders, not human rights deniers?”

A Home Office spokesperson said: “This is a sensitive and complex issue, which is why we conducted an in-depth review of protests outside abortion clinics.

“The right to protest is a vital part of a democratic society, but it is completely unacceptable that anyone should feel harassed or intimidated.

“We expect the police to take a firm stance against protesters who significantly disrupt the lives of others.”