Almost one in five people in the UK feels anxious a lot or all the time, the Mental Health Foundation said.
A survey conducted by the charity found almost half of Britons feel more anxious than they used to. Around three-fifths of the 2300 adults polled said they experience anxiety daily, with money problems the most cited cause of anxiety.
Jenny Edwards, chief executive of the foundation, said: "Anxiety is one of the most common mental health problems in the UK, yet it remains under-reported, under-diagnosed and under-treated.
"A good ability to cope with anxiety is key to our resilience in the face of whatever life throws at us. "
The charity has created a guide, Are You Anxiety Aware?, to help people understand the issue.