Plymouth police are contacting two political parties after complaints were raised about some of their general election advertising.
The Conservative party made claims in a Plymouth newspaper advertisement about how much money has been spent locally supporting the asylum system.
Police are also investigating a UKIP anti-immigration poster in Devonport.
It follows complaints from a number of organisations and people who say the items increase racial tension.
Inspector Gary Neeves of Devon and Cornwall Police’s Diversity Unit, said he was concerned about the Tory advert and its effect on ethnic minorities in Plymouth.
“We understand the need for political parties in a free and democratic society to voice their opinions.
“However, we also have to consider the impact on communities in the city.
“The advert caused distress and concern and a degree of fear among minorities in the city.”
The complaints have been recorded by the police as non-crime racist incidents.
Oliver Colvile, Conservative candidate for Plymouth Sutton ward, said: “I think there has got to be a debate about this.
“It is something that people want to talk about on the doorstep and if we don’t debate the issue we shall see a rise in the far-right parties.”
David Lott, UKIP spokesperson for the South West, said: “We are linking the question of EU immigration with whether or not we can control it.
“Obviously we will listen to what the police have got to say and people are perfectly entitled to complain.”
Karen Gillard, Liberal Democrat candidate for Plymouth Sutton, said: “I can believe this for UKIP because they are an extreme party, but I am very sad that the Conservatives have to resort to this.
“They are both trying to make out there is some kind of mass migration towards Plymouth which is not true and only goes to increase racial tension.”
A Labour Party spokesperson said: “The Conservatives have used similar tactics in many other parts of the country and we are pleased that Devon and Cornwall Police are taking these complaints seriously.
“Equally worrying is that the statistics used in these ads have been challenged on grounds of accuracy by the local authority.”
The Conservative advertisement claimed that Plymouth City Council had been forced to spend more than £1m supporting the asylum system since 1997.
But Tudor Evans, Labour leader of Plymouth City Council, has said that council tax rises could “in no way be attributed to the cost of looking after asylum seekers”.