A woman posed as the aunt of a cyclist who was killed in London in order to oppose plans for a new segregated bike lane, according to the victim’s mother.

Eilidh Cairns, a television producer from Alnwick in Northumberland, died aged 30 in 2009 after being hit by a tipper truck while riding in Notting Hill in the borough of Kensington and Chelsea.

Facebook Twitter Pinterest Eilidh Cairns. Photograph: PA

Her family was contacted by several people who attended a council meeting held this month to discuss a proposed cycle scheme in Kensington, saying a woman who spoke there claimed to be Cairns’s aunt and said: “Had Eilidh been alive today, she would not have supported the scheme.”

At the meeting, Kensington and Chelsea council announced it would be opposing the scheme because it had received 450 objections, in effect scotching it before a public consultation closed.

Cairns’s mother, Heather Cairns, has written to the council leader asking to be put in touch with the woman who “masqueraded” as her daughter’s aunt, saying: “Someone knows who she is.”

“My request to you is that you ask this person to contact me to explain her behaviour and apologise for having the effrontery to claim to know what my dead daughter would think – no one can make that claim, she is no longer here to blow out the candles on her cake and make a wish,” she wrote to Councillor Elizabeth Campbell.

She also asked Campbell to support the cycle lane, citing her own experiences as a former leader of Alnwick district council.

“Please reconsider your decision. You may lose your position as leader of the council, I did when I supported the controversial building of windfarms but I believed in the scheme and would not compromise. They were built,” she wrote.

The scheme would introduce new 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, Eilidh Cairns’s sister, an advisor on managing road risk who founded the road safety charity See Me Save Me after her death, said: “It is disappointing, shocking and irresponsible that [the borough of Kensington and Chelsea] has withdrawn support for a scheme which, had it been in place, would surely have prevented the death of my sister, Eilidh Cairns, who was run down from behind by a fully laden tipper lorry 10 years ago in the middle of Notting Hill Gate whilst cycling to work.

“She was dragged and crushed in front of traumatised schoolchildren, commuters and local shop workers. Is not her death, and a further 275 collisions on this stretch, enough avoidable destruction for the council to take action? Have our elected politicians not learned to take decisions on evidence rather than play political games?”

Will Norman, Khan’s commissioner for walking and cycling, said it was a “disgrace” for the borough to unilaterally veto a scheme on roads on which there had been 275 collisions in the last three years, with the vast majority of serious injuries being to pedestrians and cyclists.

Kensington and Chelsea council has said it will submit its own plans for alternative cycle routes to replace Khan’s scheme, which would not involve separated lanes and would send riders along back streets. There is no final timetable as to when the routes might be completed.