Scotland Yard is investigating whether a campaign targeting Stella Creasy over her views on abortion crossed the line.
The Guardian reports that Scotland Yard asked for residents in the Labour MP's Walthamstow constituency to come forward if they had footage of a billboard run by the group CBR UK before it was pulled down by the local council.
They also invited footage or material relating to two recent protests held by the pro-life group in Walthamstow that displayed posters of what the group claimed was a 24-month-old aborted baby girl.
The withdrawn billboard had shown a live foetus described by the group as being nine months old.
The materials were displayed by the group as part of its #StopStella campaign criticising her efforts to liberalise the laws on abortion in Northern Ireland and the rest of the UK.
Abortion is set to be decriminalised in Northern Ireland from October 22 after MPs in Westminster approved changes in an amendment that had been put forward by Creasy.
She said that CBR UK's campaign amounted to intimidation and harassment, and lodged complaints with the police, as well as the Speaker of the Commons and the Home Secretary.
"Any criminal conduct, any harassment, any targeting, is something we are investigating and the evidence is under review at the moment, and in due course we will seek the advice of the Crown Prosecution Service," said Supt Waheed Khan, Scotland Yard's deputy head of hate crime, at a meeting in Walthamstow organised by Creasy on Saturday.
Despite the police investigation, CBR UK has not withdrawn its #StopStella campaign and representatives of the group were out in Walthamstow again over the weekend running their display campaign and handing out leaflets.
In a statement, CBR UK has said it will continue to show graphic images in its abortion campaigns.
"We will continue to show them and will push for free speech because without being able to share disfavoured facts, social reform is impossible," the group said.
"What a chilling thought it is that Stella can use her position to silence her opposition and most of the media don't bat an eyelid."
The organisation also said it would continue targeting high profile figures on their abortion stance, including those in the Church "who remain silent on this issue".
"Stella Creasy has been an outspoken advocate for abortion, but she doesn't want people to see what she advocates for," CBR UK said.
"We are indifferent as to whether she is voted for or not. I'm sure she does a lot of good. All we want is for her to stop targeting the unborn child.
"In the future we will be focussing on four of the spheres/mountains of influence; MPs, celebrities, media outlets and churches/leading Christian figures who remain silent on this issue."