Pro-EU campaigners are encouraging hundreds of thousands of European migrants in Britain to vote in the country's European elections, in a bid to defeat Ukip and Eurosceptic candidates.

Up to 450,000 Poles, as well as Britain's sizeable diasporas of Italian, German, Spanish, Bulgarian and Romanian migrants, are being urged to vote in the May elections after UK Prime Minister David Cameron called for limits to their benefits, according to The Sunday Times.

Migrants are being sent letters stating: "This may be your last chance to vote in Britain" and "Your future and that of your family, community and friends may depend on it."

The Polish campaign, called "Vote! You are at Home", is being launched by a coalition of community groups headed by the Federation of Poles in Great Britain.

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Campaign coordinator Maciek Bator said letters would be sent to every European parliamentary candidate asking for their views on issues such as cutting migrants' benefits.

Plans are underway to deliver leaflets detailing candidates' attitudes towards Europe at polling booths on election day. Target seats are being drawn up in areas with a strong Polish presence, including Ealing in west London, Boston in Lincolnshire, Southampton and Bristol.

Mass campaigns on social networking sites, among student groups and in churches are also planned.

"We are very grateful to David Cameron for mentioning the benefit issue," Bator told the Sunday Times.

"Thanks to his words we have been able to achieve more in a short period than we were ever able to achieve in the past two and three years. He's doing a really good job for us at the moment."

Of the 450,000 Poles who have the right to vote in the UK, the Federation of Poles in Great Britain believes that only 250,000 are registered, despite the number of Poles on London's electoral role more than doubling from 41,000 in 2007 to 99,000 in 2013.

Europhile former Labour MP Roger Casale is also launching an initiative to galvanise Britain's diverse European migrant communities ahead of the forthcoming elections.

The New Europeans initiative aims to encourage migrants to register on the electoral roll and has received support from French, Greek, Slovakian, Hungarian and Austrian community leaders.

Casale's campaign will be officially launched in the House of Commons at the end of January, at an event expected to be attended by shadow police minister Jack Dromey.

According to figures from Sussex University's European Institute, the number of EU migrants registered to vote in the UK more than tripled in the 10 years to 2011, reaching 1.2m. The turnout of the last European election in 2009 was 15.7m – 34.7% of the electorate.