An American politician who has campaigned against gay marriage has been accused of having a “secret life” as a sperm donor to lesbian couples.

Bill Johnson, a 2009 conservative Christian candidate for governor of Alabama, has spent the last year in Christchurch, New Zealand, helping relief efforts in the aftermath of the earthquake.

According to the New Zealand Herald, the 52-year-old used the internet to meet at least nine women – including lesbian couples – to offer them his services as a sperm donor.

The newspaper said that three of the women were now pregnant, while Mr Johnson had donated sperm to another three in the last month.

His wife Kathy, who is unable to have children after a hysterectomy ten years ago, was unaware of his sperm donations.

According to the newspaper, he said she did not know about any of the donations and he had not planned to tell her until after the children are born.

When asked about his activities, Mr Johnson said his urge to become a biological father was “a need that I have”.

He said he did not know that some of the women were lesbians but refused to answer when asked whether this fact mattered to him.

He said: “Every person who is a father and a mother knows why I am doing this. If life’s circumstances had dealt me a different hand I wouldn’t be doing this. It is not the hand that life has dealt my wife.

“Reproduction and having children is as basic a human need as eating.”

Mr Johnson later said he had filed a complaint with police about how the New Zealand Herald obtained the information, but the newspaper says it “did not and would not use information obtained from illegally intercepted communications”.

Fertility experts have raised concerns about the extent of Mr Johnson’s donating. It is recommended that donors help no more than four families to avoid unintentional incest in future.