Britons are less honest than they were a decade ago, research by academics at the University of Essex suggests.
The survey of more than 2,000 adults found that people were apparently more tolerant of lying and extramarital affairs than they were in 2000.
But it also found less tolerance of those that commit benefit fraud.
The online "integrity" study, which repeated questions asked in 2000, suggests young people are more likely to be dishonest than older people.
In 2011, those under the age of 25 scored an average of 47 points on an "integrity scale" while those over 65 scored an average of 54 points.
The average score for all age groups was 50.
The survey also suggests women have slightly more integrity than men, but social class and occupation does not have a significant effect on levels of honesty.
Those who took part in the survey were asked to what extent a series of 10 activities were justified.
These included avoiding paying for public transport, keeping money found in the street, throwing litter and lying.
Their answers were then converted into an "integrity score" and compared to answers given by people who took the same test in 2000.
A decade ago, 70% of people said having an affair was never justified but this dropped to just 50% in 2011.
The proportion who said picking up money found in the street was never justified dropped from almost 40% a decade ago to less than 20% - while just one in three were prepared to condemn lying in their own interests.
The survey found that while 78% of people condemned benefit fraud in 2000, this had risen to 85% in 2011.
Professor Paul Whiteley, the study's author and director of the Essex Centre for the Study of Integrity, said levels of integrity were important because they were linked to a person's sense of civic duty.
"If social capital is low and people are suspicious and don't work together, those communities have worse health, worse educational performance, they are less happy and they are less economically developed and entrepreneurial. It really does have a profound effect," he said.
"If integrity continues to decline in the future, then it will be very difficult to mobilise volunteers to support the Big Society initiative," he added.
Prof Whiteley also said he thought part of the reason young people were found to be more likely to be dishonest than older people was because "the role models are not very good".
"If you think about it, you know, footballers that cheat on their wives; some journalists that hack into phones; behaviour in the City, where people are selling financial instruments they think are no good but do not say so. These kind of things," he said.