And while Dallaglio, a director at Premiership giants Wasps, has welcomed discussions, he has urged caution.
"14 seems to be a fashionable number at the moment," he said. "The southern hemisphere has gone to 15 now, but France is the Top 14.
"I think all of these things should be explored, but we have to think about the implications of everything we do.
"The important thing for English rugby is that we have a very competitive and strong domestic competition.
"We also want to have a very competitive and strong European presence within European Cup rugby and, this is probably the most important one, a strong England national team.
"Whatever decisions are made by the likes of Mark McCafferty and people who know a bit about rugby, they've got to be made in the interest of those three particular areas, not just in the interest of one particular area.
"The success of the England team is important to the success of club rugby in this country and we need to work together to ensure that whatever decision is made about numbers and competitions then it's done in the interest of English rugby."