One in three Britons believes immigration is the most important issue facing the country, a survey suggests.

The finding comes in the wake of the crisis in Calais and days before the latest official migration figures are released.

Half (50%) of those polled cited immigration as among the most important issues facing Britain.

The proportion is up by eight percentage points since July and is at its highest level, according to the latest Economist Ipsos MORI issues index.

A third (32%) of the 1,054 British adults surveyed for the monthly study said immigration is the single most important issue.

Bobby Duffy, managing director of the Ipsos MORI Social Research Institute, said:"We have never seen concern about immigration this high, and when one single issue reaches 50% it tends to signify that the public perceive that is something which needs to be addressed urgently.

"We await to see whether this 50% figure becomes a high water mark, or if consistent media attention specifically focussed on Calais pushes concern beyond this level in months to come."

Next week the Office for National Statistics will publish a fresh tranche of migration data.

The previous set showed net long term migration was estimated to be 318,000 in 2014, highlighting the challenge facing the government to achieve its ambition to reduce the figure to below 100,000 a year.

More than one in three respondents mentioned the NHS as among the most important issues.

A quarter (27%) cited the economy, a figure which has remained largely unchanged since June.

Immigration Minister James Brokenshire said: "We know that immigration is an issue which matters to the British public. Uncontrolled, mass migration makes it difficult to maintain social cohesion, puts pressure on public services, and can force down wages.

"That's why, since 2010, we have taken a wide range of measures to cut out abuse of our immigration system and to make it systematically harder for people illegally to enter, work or remain in the UK."