Agriculture Minster Simon Coveney says he can understand why some people will vote No in the upcoming same-sex marriage referendum.

There is just one week to go until polls open.

Minister Coveney - who is Fine Gael's director of elections for the referendum - says many voters will have grown up in a traditional setting and feel they want to protect that by voting No.

But he says there is nothing that undermines existing families in the extension of marriage rights to same-sex couples.