Colleagues of Labour MP Jo Cox, who was murdered in her constituency, are launching a commission in her memory to tackle the "silent epidemic" of loneliness.
The cross-party Jo Cox Commission on Loneliness will look for practical solutions to reduce the harm being inflicted on individuals, families and the wider country.
Mrs Cox had been taking the first steps towards establishing such a commission when she was murdered last June by far-right extremist Thomas Mair in her Batley and Spen constituency in West Yorkshire.
Her sister, Kim Leadbeater, said "Jo was a doer, not a complainer. We want to continue that legacy by ridding society of loneliness one conversation at a time."
The launch, at Westminster, will highlight findings which suggest loneliness is far more widespread and imposes a greater cost on those affected than previously acknowledged.
Research by the organisations supporting the commission found more than nine million people privately admit they are "always or often lonely", but two thirds would never confess to having a problem in public.
In a joint statement, the commission's co-chairwomen, Labour MP Rachel Reeves and Conservative Seema Kennedy, called for a "national conversation" to highlight the scale of the problem.
"Loneliness is a silent epidemic across the UK," they said.
"Now is the time to break that silence by starting a conversation. We need a national conversation about the scale and impact of the problem."