remain on offer ?

Should " remain on offer " be " remain on to offer "?

Context:

The non-profit International Society of Stem Cell Research in Deerfield, Illinois, has warned against so-called "stem-cell tourism", but many unproven therapies remain on offer around the world, marketed mainly through anecdotal reports of success. More information on stem cell treatments can be found on their new website.

http://www.newscientist.com/article/dn19018-game-over-for-stemcell-clinic.html