The UK needs a government-led national strategy to combat loneliness, according to a commission set up by MP Jo Cox before she was murdered.
The final report of the Jo Cox Loneliness Commission notes that nine million adults in the UK are often or always lonely and that loneliness is as harmful to health as obesity or smoking 15 cigarettes a day.
The report, published on Friday, says: "There is currently a gap in national leadership on loneliness.
"While central Government cannot solve loneliness alone, it can play a role in galvanising the key players, catalysing action, assessing and comparing progress, and holding those who need to act accountable."
In the report, the commission calls for a UK-wide strategy for loneliness across all ages, led by government "but built on the insight, expertise and capacity of many others including the NHS, voluntary and community sector and business".
As part of this, the report says, a lead minister should be appointed to drive action on loneliness across government and be accountable to parliament.
The commission also calls for a further development of the current Family Test, through which government policies are assessed to make sure they support strong and stable families, to become a Family and Relationships Test.
The report says: "Tackling loneliness is a generational challenge that can only be met by concerted action by everyone - governments, employers, businesses, civil society organisations, families, communities and individuals all have a role to play. Working together we can make a difference."
The cross-party commission was established by Mrs Cox when she was Labour MP for Batley and Spen.
Its work, which is supported by 13 charities and businesses, was carried forward after she was murdered outside her constituency office in Birstall, West Yorkshire, in June 2016.
The final report will be presented in the constituency on Friday by the joint commission chairs, the Labour MP for Leeds West, Rachel Reeves, and Seema Kennedy, the Conservative MP for South Ribble.
The MPs will be joined by Jo's sister Kim Leadbeater.