Migrant voters could directly impact who is elected to represent Gloucester in this year's General Election.
According to a study by Manchester University and the Migrants' Rights Network nearly four million people eligible to vote in May's election were born overseas and they could have a "decisive" impact in key marginal seats including Gloucester.
Conservative Richard Graham, the current MP, is getting ready to face Labour candidate Sophy Gardner, UKIP's Richard Ford, Liberal Democrat Jeremy Hilton and Green's Jonathan Ingleby.
In the 2010 election Mr Graham stole the seat from sitting Labour MP Parmjit Dhanda – but only with a slight majority of 2,420 votes.
The report highlighted a challenge for the Conservatives, particularly over migrant voters, while noting that generations of migrants had formed an image of Labour as the party that 'protects migrant and minority interests'.
It also warned that negative messages about immigration could alienate these people before the vote on May 7.
Speaking on BBC Radio 4's Today programme the co-author of the report Ruth Grove-White, said: "In a small number of marginal seats, the migrant vote really could be decisive.
"We know that migrants in the UK are much more positive about immigration and its cultural and economic impact, and much more likely to be concerned about racial discrimination.
"Politicians need to be careful. This is an election which has been characterised by a very heated debate about immigration. It's very easy to forget that politicians are also talking to migrant voters as well."
Most migrant voters come from established Commonwealth communities - India, Pakistan, Bangladesh, Nigeria and South Africa - as well as the Irish Republic.
In contrast, the report said, European Union nationals living in the UK will be "heavily under-represented" because a large majority have not acquired British citizenship.
