In England, more than 1.2 million men aged over 50 reported a moderate to high degree of social isolation, with 710,000 men aged over 50 reporting a high degree of loneliness.
The joint report by Independent Age and the International Longevity Centre-UK (ILC-UK) shows that older men are more socially isolated than older women - one in three compared with one in five - and have less contact with their children, family and friends than older women.
The new research also reveals that older men's social networks tend to decline after the death of a partner. Poor physical and mental health is much more likely for the most socially isolated, and lonely older men are less likely to seek help or ask for support.
Nathan Blackaby from Christian Vision for Men believes males should be investing more time in friendships with other men.
Speaking to Premier, he said: "Something we're seeing is that guys are not quite making the connection, the friendships that we want to see. As guys we need to connect with other guys; we need to share our lives with other guys. When their partner dies they find themselves looking around saying: 'Where are my friends? Where are my support networks?'"
Hear more from Nathan Blackaby at Christian Vision for Men: