Nigel Farage has blamed "people who do not speak English" for Ukip's heavy by-election deafeat at the hands of Labour in Oldham West.
The Ukip leader, who also labelled postal voting in the election "bent", said that non-English speakers in the constituency were signed up to vote by post - and that this explained the size of Labour's win.
Labour's candidate Jim McMahon increased the party's share of the vote in Thursday's poll, from 54.8 to 62.2 per cent, romping home with a majority of more than 10,000 over the UK Independence Party's John Bickley.
Speaking to the FT after the result, Mr Farage said of postal voters: “They don’t speak English. Ukip does not get votes from people who do not speak English.”
Postal voters, some from the town's large Pakistani and Bangladeshi communities, made up a quarter of the electorate in the Oldham West and Royton by-election.
Mr Farage expanded on theme on Friday morning, as Ukip announced it will file a formal complaint over alleged "abuses" in the election.
Mr Farage told BBC Radio 4's Today programme: "There are some really quite big ethnic changes now in the way people are voting. They can't speak English, they have never heard of Ukip or the Conservative Party, they haven't even heard of Jeremy Corbyn.
"I'm commenting on the state of modern Britain, post mass immigration. It means effectively that in some of these seats where people don't speak English and they sign up to postal votes, effectively the electoral process is now dead."
Evidence from an impeccable source that today's postal voting was bent.— Nigel Farage (@Nigel_Farage) December 4, 2015
Mr Farage said he was not questioning Labour's victory, but denounced the electoral process after claims that people had arrived at polling booths carrying bundles of postal votes.
Ukip deputy leader and North West MEP Paul Nuttall claimed postal voting had "distorted" the result, a claim denied by Labour.
Additional reporting by Press Association