The survey results show that 45 percent of those polled said that immigration was the most important issue facing Britain, overtaking the National Health Service, which topped the Ipsos MORI opinion polls in January and February.
The economy, unemployment and education rounded out the top five biggest concerns of the British public in March, the survey suggested.
Ipsos MORI, a leading market research company in the United Kingdom, provides a monthly overview of key issues concerning the country. Over 1,000 adults from across Britain took part in its latest survey.
Net migration is the difference between the total number of migrants entering the country and leaving it.
Britain's immigrant population grew by almost 300,000 people in the year ending September 2014, despite Prime Minister David Cameron's pledge in 2011 to reduce it to "tens of thousands."