Festival of Light Australia, a national Christian and family advocacy group, is urging all political parties and candidates in the country to take the opportunity on Australia's Father's Day to declare their position on fatherhood.

"Fathers are essential to the welfare of the nation," said Richard Egan, national policy officer for Festival of Light Australia.

"All the research evidence shows that children - both boys and girls - flourish best in education, social behaviour and their own future marriages and family life when they are raised by Dad as well as Mum, especially when Dad has expressed a lifelong, public commitment to their Mum in marriage," Mr Egan said.

He urged political candidates to declare their policies on fatherhood and marital issues as Australia's federal elections approach: "We are calling on all the political parties and candidates to declare their position on fatherhood and marriage leading up to the federal election.

"We will be surveying all parties and candidates on ten questions, two of which deal with marriage: 'Would you vote to amend the Marriage Act 1961 to prevent states from giving legal recognition to couple relationships other than marriage, including homosexual, lesbian and de facto relationships?' and 'Would you oppose any measures that sought to extend to homosexual and lesbian couples the benefits currently given to married couples?'" Mr Egan said.

Mr Egan said that marriage in the biblical sense of one man and one woman was the most fruitful way to provide a healthy family environment for children: "Giving benefits to same sex couples, or granting them legal recognition alongside marriages in an official marriage register undermines the unique status of marriage.

"Marriage involves the complementarity of one man and one woman - united for life. This is the best environment for raising children who need a dad as well as a mum."

Underlining the importance of maintaining the uniqueness and sanctity of marriage, Mr Egan added: "We need to do everything we can to strengthen marriages. Treating marriage as just another relationship alongside de facto, male homosexual or lesbian relationships undermines its importance to society. Ultimately it puts more children at risk of fatherlessness, and all the problems that flow from lacking a father."

He concluded saying: "This Father's Day, let's all agree to make sure that the next generation of Australian children can celebrate this day with joy and gratitude for their fathers."