Nigel Farage’s Ukip has called for the children of immigrants to themselves be classed as migrants – despite the fact that the party leader’s own two children would be included in that number.

The party highlighted a report issued today by the right-wing thinktank MigrationWatch UK, which said immigration’s impact on population growth had been underestimated by more than 1.3 million because babies of those coming to this country were not taken into account.

Neither MigrationWatch nor Ukip suggested that the citizenship of those born in Britain was in question.

But Mr Farage, whose wife is German, tweeted his own concerns that “84 per cent of population growth between 2001 and 2012 – or 3.8 million – was due to migration” – if you include children born here in the statistics.

Other Twitter users suggested this is the case “only if you count your kids as migrants, dear Nige”, and that by this definition “Winston Churchill and Prince Charles are immigrants”.

A spokesperson for Ukip said that while Mr Farage would never talk about his own children “either way”, the issue of “hiding” those born to migrants from statistics had “ramifications for healthcare and other public services”.

“We have to accept that this is happening because otherwise you can’t make the decisions to make sure everyone is OK,” the spokesperson said.

“If the figures for migration don’t include children, you’re not taking the correct facts into account for public policy.”

The Office for National Statistics, which provides Britain’s official population figures, says it does not define children born in the UK as immigrants “in accordance with UN international standards”.

Ukip's spokesperson insisted that it is “not the children that are the problem, it is hiding them that’s the problem” – adding that the issue “didn’t matter” for figures like Churchill or the heir to the throne because when their parents came over immigration “was such a small number”.

The comments come in stark contrast to those made yesterday by Labour’s policy chief Jon Cruddas, who said immigration is “not a numbers game”.

In pictures: The rise of Ukip Show all 8 1 /8 In pictures: The rise of Ukip In pictures: The rise of Ukip 1993: Alan Sked forms Ukip History professor Alan Sked had been active in anti-EU politics for a while beore he founded Ukip in 1993. He resigned from the party after the 1997 election, concerned that it was attracting far-right members, and has been critical of Ukip since. Picture: Reuters Reuters In pictures: The rise of Ukip 2005: Kilroy defects Former TV presenter Robert Kilroy-Silk founded Veritas in 2005, after a failed bid to become leader, and took many of Ukip's elected members with him. But the party slowly lost its popularity and didn't put forward any candidates in the last election. Picture: REUTERS/Kieran Doherty REUTERS KD/RUS In pictures: The rise of Ukip 2010: Farage becomes leader, again Farage had led Ukip from 2006 until 2009, when he stood down to fight against the Speaker, John Bercow, for his Buckingham seat. He failed to win the election and returned to lead the party in November 2010. Picture: REUTERS/Kieran Doherty REUTERS/Kieran Doherty In pictures: The rise of Ukip 2010: Ukip fights for election Nigel Farage was injured in a plane crash on polling day in the 2010 general election, but his party increased its success in the votes. It fielded 572 candidates and took 3.1% of the vote, though failed to win any seats. REUTERS/Darren Staples REUTERS/Darren Staples In pictures: The rise of Ukip 2013: Eastleigh gains Ukip's candidate Diane James got the highest ever number of votes for any candidate from the party, but was beaten by the Liberal Democrats. The surge in support gave Ukip confidence ahead of local and European elections later in the year. Picture: Reuters In pictures: The rise of Ukip 2013: Bloom kicked out Godfrey Bloom, who served as an Ukip MEP from 2004 to 2014, had the whip withdrawn in 2013 after sexist comments and an attack on a journalist. He sat as an independent MEP until 2014, when he ended his term in office. Picture: REUTERS/Luke MacGregor In pictures: The rise of Ukip 2014: European election success Ukip got a higher proportion of the vote than any other party in 2014's European elections, adding 11 new MEPs and taking its total to 24. REUTERS/Luke MacGregor In pictures: The rise of Ukip 2014: Carswell defects Douglas Carswell defected from Ukip at the end of August, and was followed by Mark Reckless at the end of September, who resigned from the Tories amid rumours of many more defections to come. Picture: REUTERS/Toby Melville

Speaking at an event in the Commons, Mr Cruddas said Labour would address the issue of immigration by showing people they do lose out as a result of the new arrivals.

He said: “It seems to me it's about building confidence around our ability and our agility in terms of the public policy we are making so that you can reassure people that it's not materially at their expense.”