The mother of murdered teenager Brianna Ghey said she was "devastated" to learn the prime minister had met social media bosses about online safety issues before talking to bereaved families.
Sir Keir Starmer held a meeting with bosses at Google, TikTok and Meta earlier this month, urging them to "work with us to do better by British children".
In an open letter to Sir Keir with 12 other families, Esther Ghey said they had an "unwavering" resolve to stop others "enduring the pain" they felt, adding it was of "equal importance" he heard from them.
The government said it "shares Esther Ghey's determination to keep children safe online", adding: "This is a complex issue with no overall consensus."
The prime minister has been meeting families and young people to discuss the future of social media and its impact on children, and will continue to engage with families who have been directly affected, a spokeswoman added.
Ghey told BBC Breakfast: "I thought we would be the first ones to meet the prime minister.
"We deserve to be listened to.
"This is why I was so disappointed as it is so important to speak to lived-experience campaigners before multi-billion pound companies.
"We are not being listened to - we are desperate to be heard."
Ghey has been campaigning for social media and mobile phone restrictions for children after her 16-year-old daughter Brianna was killed by two teenagers in a Warrington park in 2023.
One of the killers said she had become interested in "dark materials" including online videos of murder and torture.
In 2024, Ghey spoke about youth mental health issues with Sir Keir - before he became prime minister - and said she had "greatly appreciated" the discussion.
"It is in that spirit that I, and other bereaved families, are requesting a meeting so you can hear first-hand why it is so urgent that governments act to protect children and young people," she said in the open letter.
"While we, as bereaved families, may not have the financial influence of large corporations, what we do have is an unwavering determination to ensure no child or parent has to endure the pain and suffering we experienced."
She added: "While we understand the importance of engaging with industry, it is of equal importance that you hear directly from those who have experienced the devastating consequences associated with online platforms."
The government responded: "We have launched a consultation looking at everything from age limits and safer design features on AI chatbots and games, to a social media ban.
"We're also running pilots with hundreds of UK families and engaging with parents, children and experts to make sure we get this right."
Technology Secretary Liz Kendall had met with the Bereaved Parents for Online Safety group earlier this year and had since held further discussions with bereaved parents, it added.
The three-month government consultation on social media restrictions for youngsters has received more than 45,000 responses since its launch in March.
While plans to prevent children's usage have drawn support from many quarters, others warn that youngsters could circumvent the ban or be driven to darker corners of the internet.
Earlier this month, MPs voted for the third time to reject a social media ban for under-16s.
A recent survey found many children aged 12-15 still had social media access in Australia, despite the country having introduced the world's first ban for under-16s in December.
In March, a US court jury found that Google - which also owns YouTube - and Meta, which operates Instagram, Facebook and WhatsApp, intentionally built addictive social media platforms.
Both firms disagreed with the verdict, which they plan to appeal.
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