The Labour MP Stella Creasy has contacted the police and said she feels “physically sick” after being targeted by an anti-abortion group.

Creasy, who represents Walthamstow in parliament, expressed her concern as protesters entered her constituency and put a poster of her next to a picture of what it claimed was “a 24-week-old aborted baby girl”.

The image reads: “Your MP is working hard … to make this a human right.” It also has the address for a website that has been set up against the MP.

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The protest and campaign was set up by an 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.

Creasy reported the campaign to the police. In a tweet she said: “Feel physically sick.” She added that the police said they would not use PSPO [public spaces protection orders] powers – used when a particular nuisance in a particular area that is having a detrimental effect on the quality of life – to move the protesters on.

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.

The mayor of London, Sadiq Khan, described the action as “sickening”. In a tweet, he said: “Whilst the right to peaceful protest must be respected, behaviour that deliberately targets women for harassment and intimidation should not be tolerated.”

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

The website, which has been 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.”

Ruth Rawlins, a spokesperson for CBR UK, said: “By removing sections 58 and 59 of the Offences Against the Person Act, [Creasy] will remove all legal protection for the unborn child up to 28 weeks. This is a human rights abuse which needs to be called out. We have come to Walthamstow to communicate this to her constituents.

Creasy’s amendment argued that abortion laws in Northern Ireland, where women seeking a termination 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 – the best of what this place does – as human rights defenders, not human rights deniers?”

After the vote, Creasy tweeted: “Thank you to everyone who today stood up for equality in Northern Ireland – whether for same-sex marriage or abortion, today we have said everyone in the UK deserves to be treated as an equal. There’s a road to go yet but today a big step forward.”