The proportion of people who say they are middle-class has risen by nearly half in 40 years, a report says.
Is it upbringing or income which makes people middle class?
Forty-three percent of people surveyed said they were middle-class, compared with 30% of people in 1966.
But most - 53% - said they were working-class. The report also suggests that many are confused about which class they belong to.
The survey, carried out for the Liverpool Victoria Friendly Society, saw 1,000 people interviewed in March.
Conducted by the Future Foundation, the survey found that 36% of builders questioned regarded themselves as being middle-class, while 29% of bank managers said they were working-class.
The results suggest that about 2.67m people consider themselves working-class even though they are among the top 20% of richest Britons, as do 500,000 who earn more than £100,000-a-year.
The survey found that people who said they were middle-class had twice the level of savings and three times the level of investments as those who said they were working-class.
While both classes have similar levels of home ownership, middle-class people live in properties worth an average 70% more than those owned by working-class people.
Just under a third of both groups thought upbringing and job was important in determining class.
However, working-class people were more likely to place an emphasis on income, while middle-class people tended to cite education and the house and area you live in as being important factors.
Economist Bruce Anderson said the change was good for society. He told BBC News that more people regarding themselves as middle-class meant more people with wider horizons.
"So I think it is a good thing for society. In all societies the middle-classes provide the bedrock of stability."
'Choose a side'
Researchers also found that working-class incomes were now at the same level as middle-class incomes were in the 1980s.
But the average middle-class Briton still had £100,000 more individual wealth than a working-class counterpart.
However, Neil Lawson, of left-wing think-tank Compass, said income was not the best way to measure class.
He said: "There's a big difference between how people perceive themselves and the reality of their income, if you want to measure class by income.
"I don't really think that's the definition for me. I think if people use their hands or their brains to work, then they're pretty much working-class."
Report author William Nelson said the researchers found both middle and working-class people thought they worked harder than the other, but neither saw themselves graduating to upper-class.
"About 90% of the population will feel that they are a member of a particular class, be it middle-class or working-class. Almost nobody thinks they're upper-class.
"To that extent I think we all, in our heart of hearts, have to choose a side to be on, you might say."