Veteran Labour MP Austin Mitchell has dismissed Ukip’s chances of winning the Great Grimsby constituency at the general election, saying that Labour would win the hotly contested seat “even” if it had selected a “raving alcoholic sex paedophile” as its candidate.

The long-serving Labour MP, who is stepping down at the election, has represented the constituency in north Lincolnshire since 1977 and Labour has held it since 1945, but Nigel Farage’s party polled strongly in the area in recent local elections and in the 2014 European election, while a recent Lord Ashcroft poll suggested it only trailed Labour in the seat by one per cent.

In an interview with The Independent on Sunday focusing on the Great Grimsby seat, he said: “There is no chance we'll lose Grimsby, even if we selected a raving alcoholic sex paedophile we wouldn't lose Grimsby”

He added: “I don’t think there is a problem in Grimsby. There will certainly be a rise in the UKIP vote now that they have a councillor and did quite well in the European elections. But when it comes down to it their vote isn’t concentrated enough to win any seats.”

Mr Mitchell’s parting shot from the constituency was quickly seized upon by the Ukip candidate Victoria Ayling, who came within 714 votes of defeating Mr Mitchell in 2010 when she stood as a Conservative candidate before her defection to Ukip.

She said: “It’s insulting to the great people of Great Grimsby. And it’s exactly the sort of ‘take them granted’ attitude that is turning people away from the establishment parties. Austin Mitchell has been a respected constituency MP but he’s assuming that people don’t think very carefully about how they vote. People do think very carefully and I don’t like Mr Mitchell insulting the people of Grimsby.”

Labour’s candidate for the seat, Melanie Onn, was clearly exasperated by her party colleague’s intervention, describing them as “awful”.

The seat is seen by as key indicator of whether Ukip can take voters of Labour in the north of England, though the area has seen little immigration and the last census put the population as 96 per cent white British. However the latest Core Cities report shows the town is a youth employment black spot and suffering from stagnating population growth.

Mr Mitchell went on to call Ms Ayling a “wonderful candidate” but said she would struggle because the people of the town would view her as a “turncoat” due to her defection.