The "social epidemic" of loneliness needs to be tackled by a combination of government intervention and "every single one of us" playing our part, according to the sister of murdered MP Jo Cox.
Kim Leadbeater was speaking after a commission set up by Mrs Cox before her death recommended that the UK needs a government-led national strategy to combat a problem which affects millions of people.
The final report of the Jo Cox Loneliness Commission found 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.
And it detailed how three-quarters of GPs say they see up to five patients every day who are lonely and that loneliness is estimated to cost employers £2.5 billion every year.
Ms Leadbeater said: "Yes, government has got to play a part, that's where policies are made and that's where some of the money's going to come from. But the great thing about this issue is that we can all make a difference.
"We can all go out tomorrow and knock on somebody's door, catch up with a friend we've not seen for a while who might be having a tough time and we can all make a little bit of difference."
Speaking following the report launch in Batley, West Yorkshire, Ms Leadbeater said: "On a day-to-day basis it needs to come from us - every single one of us.
"I'm really embarrassed that I didn't know my neighbours until Jo got killed.
"And I know everybody on my street now. Because what they did, they scooped me up and looked after me when I needed it, and that just shows you the power of community."
Ms Leadbeater said her sister developed an interest in loneliness when she found herself feeling alone as a student at Cambridge University.
She said: "We all have this outside persona that everything's great and we're having this fantastic time but often it's not like that.
"Jo (pictured) and I were really close when we were growing up - we did everything together as kids.
"When she went away to university, she entered this world of Cambridge, which was a very intimidating place for a working class northern girl."
But Ms Leadbeater said her sister would have wanted the report to move from words to action.
"Talking about things is fantastic but let's get on with it," she said.
The cross-party commission was established by Mrs Cox when she was Labour MP for Batley and Spen.
Its work, 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 was presented in the constituency on Friday by Ms Leadbeater along with the joint commission chairs, the Labour MP for Leeds West, Rachel Reeves, and Seema Kennedy, the Conservative MP for South Ribble.
Earlier this week, Ms Reeves described loneliness as having "escalated from personal misfortune into a social epidemic".
The report calls for a government UK-wide strategy for loneliness across all ages with a lead minister appointed to drive action.
A Government spokeswoman said: "We welcome the work of the Jo Cox Commission and its ambition to combat loneliness. Tackling social isolation and loneliness is of huge importance to the Government.
"A number of Government initiatives already help to reduce loneliness, such as improved mental health support and funding to create new green spaces for communities, but we are committed to doing more and look forward to setting out plans in the New Year."
The Royal Voluntary Service (RVS), the charity Jo Cox's family chose to receive funding to continue her legacy after she was murdered, is launching three new projects in her former constituency to help reduce loneliness and isolation, particularly amongst older people.
RVS Chief Executive Catherine Johnstone said: "As Jo Cox said 'loneliness doesn't discriminate' and over the course of the last year we have had our eyes opened to just how many of us are affected. We welcome the commission's manifesto and agree that whilst the government has a role to play, tackling loneliness is the responsibility of all of us."
Copyright (c) Press Association Ltd. 2017, All Rights Reserved. Picture (c) Jo Cox Commission / PA Wire.