A further one in ten said they were considering reducing their meat intake or cutting meat out completely, according to questions commissioned by the Vegetarian Society.
The report also states that nearly half (44%) of people either do not eat meat, have reduced the amount of meat they eat or are considering reducing the amount of meat they eat.
Lynne Elliot, chief executive of the Vegetarian Society, said: "We commissioned this research because, for some time, we have noticed people are positively engaging with the idea of eating less meat, but until now there has been little academic evidence to support this.
"This report very much reflects what we see every day in our work: that there is an increasing awareness of the issues relating to our food choices, and that has resulted in a large number of people reducing the amount of meat they eat or cutting it out altogether.
"Vegetarian options are an easy, healthy and tasty way to eat – and it's clearly an option being enjoyed by a large section of the population."
The analysis found that over a third of women (34%) and nearly a quarter (23%) of men had reduced their meat intake in the last year. Older people (65 to 79 year olds) were twice as likely to have reduced their meat consumption as 18 to 24 year olds (39% compared to 19%).
As well as asking people about their meat-eating habits, researchers also asked people who had given up meat, reduced their intake or were thinking about doing so, what had influenced their decision. People were asked to pick reasons from a list and could give as many reasons as they liked.
'Health reasons' was by far the most common reason given for consuming less meat, cited by over half (58%) of people in this group. Other reasons for reducing meat consumption included 'saving money' (mentioned by 21% of people), concerns over animal welfare (mentioned by 20% of people), and concerns around food safety in relation to meat (mentioned by 19% of people). Around one in ten (11%) people in this group mentioned 'environmental concerns' as a reason for reducing their meat intake.
Ian Simpson, Senior Researcher at NatCen Social Research said: "A significant number of people in Britain, amounting to many millions, told us that they have reduced their meat consumption over the past 12 months. Many people in Britain are clearly concerned about eating too much meat and the primary driver of this concern appears to be concerns about health.
“High-profile news stories, like research highlighting the health risks of processed meat and the horse meat scandal, could be behind this behaviour, as may Department of Health guidance around reducing meat consumption. Since we collected the data, the World Health Organisation has classified processed meat as carcinogenic, suggesting we may see even more people cutting down on meat in the future."
To view the full report, click here.