Cox was murdered last week in the street outside of her constituency surgery in Birtsall, West Yorkshire. Since then, several political parties have said they will not contest the seat out of respect.
The Conservatives were the first to rule out fighting the by-election, and the Liberal Democrats, Ukip and the Green Party have all since ruled themselves out.
However, former BNP member Jack Buckby has today announced that he will fight Labour for the seat.
Buckby will seek election for “anti-Islamisation” party Liberty GB.
The party lists as its main aims as "halting the Islamisation of Britain" and "promoting British values and assimiliation rather than multiculturalism".
In a statement announcing his plan to stand, Buckby said: "While the murder of Jo Cox is tragic, we must not let this tragedy blur the fact that the Labour Party is responsible for the demographic and cultural assault on Britain which has already done great damage in areas of Yorkshire.
"Too much is at stake to allow Labour to retake Batley and Spen unchallenged. The constituency is part of a region that has been turned upside-down by mass immigration, with mosques sprouting like triffids, Islamic extremism proliferating, child-rape gangs still on the loose, and long-standing English communities under threat of demographic eradication."
A date for the by-election has yet to be set.