Text not in the screengrab above referred to a planned march in Birmingham by the group and said “several bombs will detonate and those who will march be dead (sic)”.
It also ordered the group to “stop being racist to Muslims” and warned “whoever goes to the march will die”.
The offending text has been removed and the website now consists of just a homescreen.
Personal details including addresses of the pair were also posted online.
The latest video posted by the group on YouTube about an incident in Birmingham earlier in the week appears to have been taken down by the platform for violating “harassment and bullying” guidelines.
But all other videos lead to a links saying they have been “removed by the user”.
All 178 videos on the channel have been affected.
The perpetrator of the hack is not yet known.
Britain First has been contacted for comment.
The far-right group made headlines earlier in the week when they and former leader of the English Defence League (EDL) were in Birmingham, a city they have dubbed the “Jihadi capital of Britain”.
Fransen and Golding tell the camera they are “very proud” to be holding the cross during Holy Week despite previously being condemned as “un-Christian” by every single Christian denomination in the UK.
An edited video posted by the group shows them being attacked with eggs in a white van and leaving Birmingham “in haste because we were surrounded by about 30 Muslims... and it got violent very quickly”.
But another video broadcast live on Facebook at the time tells a slightly different story as to why they left in such a hurry.