The family of a woman killed cycling in London say they have identified the woman they accused of pretending to be the victim’s relative in order to oppose new protected cycle lanes in London.

Eilidh Cairns, a 30-year-old TV producer from Alnwick in Northumberland, was killed by a tipper truck in Notting Hill in the borough of Kensington and Chelsea in 2009.

On Monday, Eilidh’s mother, Heather Cairns, wrote to the leader of the council to ask her to find the woman who was “masquerading as the aunt of Eilidh Cairns” at a public meeting about a controversial new cycling scheme on 13 June.

After the Guardian published extracts of the letter, the family managed to track down the woman. She is a non-blood, distant relative they insist they have never met and whom Eilidh would not have known either.

They were originally told the woman had claimed to be Eilidh’s aunt, but after listening to a patchy recording of the meeting it sounds like she simply claimed to be a “relative”.

Kate Cairns, Eilidh’s sister, a road safety campaigner and an advisor on managing road safety risk, said the woman mispronounced Eilidh’s name. She transcribed the recording and says the woman said: “It’s difficult for me not to be emotional because Elodie [sic] Cairns was a relation of mine and I totally disagree with this scheme …

“It’s going to be dangerous and I’m sure Elodie [sic] would be very upset with the very thought of such a stupid idea coming forward.”

At that meeting, Kensington and Chelsea council said it would be opposing the scheme, which would introduce pedestrian crossings and install protected bike routes along some of inner London’s more dangerous roads, including Notting Hill Gate and Shepherd’s Bush. It was being planned by the office of the London mayor, Sadiq Khan, and Transport for London (TfL) but the local authority had an effective veto because it would run on council roads.

Kate Cairns said the woman in question used her sister’s name “to give credence and authenticity to her own personal views”, which she insisted were “completely contrary and conflicting to those of all Eilidh’s family and all of her close friends”.

She said: “[The woman’s] own personal views are strong and scathing against a scheme which would have saved Eilidh’s life. [She] has been opportunistic and exploitative in claiming to be a ‘relative’ in order to mislead and manipulate those present by implying closeness and connection with the family but a) she does not even know how to pronounce Eilidh’s name b) she has never met Eilidh, nor me c) she is not known to my mother, Eilidh or me and d) she is not in touch with Eilidh’s close family and indeed did not inform us about the meeting, nor that she was planning to attend.”

She added: “One would expect someone so upset and living so close when the family are so far to perhaps have laid flowers on Eilidh’s birthday, and death day. We have never heard from her, ever, despite public celebrations, family meetings and memorial bike rides at the spot of Eilidh’s crash.”

Eilidh Cairns died in February 2009. Photograph: Family Handout/PA

In an email to Cllr Elizabeth Campbell, the leader of the Royal Borough of Kensington and Chelsea (RBKC) council, seen by the Guardian, the woman said she had made a mistake. “I regret having suggested what Eilidh might think of the scheme – it was not my place to give her view although I stand by my claim that the scheme is ill thought out and dangerous for pedestrian and cyclists,” she said.

An RBKC spokesman said Campbell had written a letter back to Eilidh’s mother on Tuesday.

Asked whether the council would rethink its opposition to the cycle scheme, the spokesperson sent this quote from Cllr Johnny Thalassites, the lead member for transport and planning: “For me, protecting the people using or living near our roads is absolutely vital – that’s why we’re planning a range of cycle routes that will help people to move safely on our streets without causing congestion or making poorly thought out changes to local streets that people rely on.”