United States soft-rock band Train are "upset" after their song Marry Me was used in a New Zealand anti-gay marriage website.

Family First website Protectmarriage.org.nz featured the music video for Marry Me, but the San Francisco-based band was alerted to its use by a New Zealander through Twitter.

Train has now released a statement saying "it was upsetting to us that Marry Me, a love song with no boundaries, was being used to promote an agenda we don't subscribe to".

"We [Train] take the idea of marriage very seriously, and believe it is the right of all consenting adults, regardless of sexual orientation.

"Marry Me is about just that, finding that special love and making it last forever. Everyone should be allowed to have that."

It is not the first setback to Family First's anti-gay marriage campaign. The website had to be taken down after "unprecedented attack" took out the website's host servers on its Monday launch.

Family First director Bob McCroskrie said the website was dedicated to opposing Labour MP Louisa Wall's Marriage Equality Bill, which was pulled from the ballot last week and had sparked heated debate from both sides.

While the site was reinstated a couple of times on Monday, its Christchurch-based webhost had to eventually pull the site completely because hackers had overwhelmed their servers so much it affected every other website hosted by the company.

Family First's own website was also hosted by the company and also had to be pulled, but both sites were now back up and running on international servers.

"It is disappointing that some opponents in the marriage debate are unwilling to have robust debate and are resorting to desperate - but failed - attempts to shut us down," McCroskrie said.

"We are also disappointed that our web host company was targeted with offensive emails simply because they were a Christchurch business that we wanted to support and who were willing to host some of our websites."

Train have been working at getting their music video removed from the site since Monday, and just today it has been taken down.

Train caught wind their song was being used by Family First after a Twitter user alerted the band their song was being used on an "anti gay marriage website".

A user named @Mikey_J_S6 tweeted the band last night saying: "Why does your music video appear on a homophobic lobby group's website?". Train responded saying "Didn't know. Getting it off asap. Tnx 4 tip".

McCroskrie said earlier in the week they had not yet heard from Train, but if they were asked to take the song down they would.

- © Fairfax NZ News