The National Rugby League has answered a call from former international Ian Roberts to endorse same-sex marriage.

Roberts, the former Souths, Manly and Cowboys prop who came out publicly during the 1990s, wrote a letter to chief executive Todd Greenberg last week, imploring him not to "miss this moment in history".

After being approached by former player Ian Roberts, the NRL is supporting same-sex marriage. Credit:Kate Geraghty

Greenberg responded on Friday, saying he recognised the right of all Australians to make their own decision on how to vote in the poll, which begins next Tuesday when ballots are mailed to millions of households.

"But one of the key pillars of rugby league is inclusiveness – and the game has a duty to back up its policy with action," Greenberg said. "There is a place for everyone in rugby league. It might be as a junior, as a volunteer, as a match official or as an NRL player. And we need to treat everyone equally both on and off the field and that's why we will publicly support the same-sex marriage proposal."