Therese Hirst, the party’s deputy chairman and former leader of Veritas, will stand in the by-election, which is not being contested by the Conservatives, Liberal Democrats or Ukip.
The party, whose slogan is “Putting England First”, said it was “only right that voters should have a choice” as they revealed Ms Hirst as their candidate.
Last month, Liberty GB were the first party to announce that they would contest the by-election with former BNP member Jack Buckby.
An English Democrats spokesman said: “We felt it was right to wait until after Jo Cox’s funeral, before making the announcement.
“We wanted to be respectful, but we think it is only right that voters should have a choice, and as far as we are concerned this is a democracy and we felt we ought to stand.
“This is about what the people of Batley and Spen want to vote for. We will be giving them a pro-Leave (Europe) candidate whereas we think Labour will put forward a Remain candidate.”
The party describes itself on its website as “not left, not right, just English”, but it also carries a section called “Labour - The new nasty party?” and an article headlined “‘London is in trouble’ for voting Muslim Mayor Sadiq Khan”.
Mrs Cox died last month after being shot and stabbed outside a library in Birstall, West Yorkshire.
Her funeral was held in her constituency on Friday last week and hundreds of people lined the streets to pay their respects to the mother of two young children.
• Thomas Mair, 52, has appeared at the Old Bailey in central London charged with murdering Mrs Cox.
He is also charged with grievous bodily harm, possession of a firearm with intent to commit an indictable offence and possession of an offensive weapon. At an initial hearing at Westminster Magistrates’ Court, Mair refused to give his name, instead saying he was called “Death to traitors, freedom for Britain”.
He was remanded in custody and is due to go on trial in November.