East Sussex BNP leader Nick Prince criticised Greg Barker for coming out after he had won a seat in the 2005 general election.
Mr Prince added that he believe the BNP could topple Mr Barker, who has a majority of 13,449 votes. The Rother area has only 36 BNP members.
The candidate who will challenge the sitting Tory MP is Neil Jackson, 51. He was named as the BNP candidate for the seat last week.
Mr Prince, who is contesting the nearby Hastings seat, told the Bexhill Observer that his party would not allow men to kiss in public or gay couples to adopt children.
He then criticised Mr Barker, who was married with children when he came out in 2006
Mr Prince said: "In the case of Greg Barker, it is a question of morals and honesty. He went to the electorate a married man with a nice young family – now he goes to his electorate five years later a homosexual man.
"I don't believe it to be homophobic to raise this issue when we are talking about a guy in his early forties – it is a little late in life to be confused."
Mr Barker told the newspaper he did not intend to enter a slanging match with the BNP. He said: "The BNP is completely beyond the pale and I have no intention in entering into a debate with that sort of people."
Last week, BNP leader Nick Griffin suggested that he had made his party more gay-friendly.
Speaking to Total Politics magazine in extracts published by PinkNews.co.uk, he said that he knew the party had gay members but that it was a "don't ask, don't tell situation".
Mr Griffin said the party had moved away from wanting to re-criminalise homosexuality but would scrap civil partnerships if it got into power.
Pink News
