Nigel Farage will visit South Thanet the day after charges were brought against Tory Craig Mackinlay
The decision to return to his old battleground came after the Crown Prosecution Service charged Craig Mackinlay over election expenses in the vote.
Mr Mackinlay has denied the claims, saying he has done nothing wrong.
Nigel Farage lost the seat to Mr Mackinlay in 2015
Theresa May has thrown her support behind Mr Mackinlay, saying: "The Conservative party continues to believe that these allegations are unfounded.
"Craig Mackinlay is innocent until proven guilty and he remains our candidate."
There will be questions
But the decision drew criticism from Mr Farage.
He said: "Once again it is bad judgment from Theresa May.
"Why on earth would you allow someone to go ahead as General Election candidate when this cloud was clearly hanging over him? There will be questions."
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Nigel Farage in pictures Mon, April 3, 2017
Nigel Farage is a British politician who has been the leader of the UK Independence Party since October 2016.
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Nigel Farage in pictures
He is expected to give a speech in the Kent constituency in support of Ukip candidate Stuart Piper.
Asked whether the decision would benefit Ukip, which is currently picking up five points in opinion polls, Mr Farage said: “Yes. I think it does help Ukip.
“There is no reason why we can’t nick a few seats.”
Theresa May rushed to the defence of Mr Mackinlay
Mr Farage attempted seven times to win a seat in Parliament before standing down as Ukip leader following the European Union referendum.
His successor Paul Nuttall is campaigning in the Lincolnshire seaside town of Skegness, where he is hoping to be elected MP for the Ukip target seat of Boston and Skegness.