Tait, England's outside centre in both autumn Test appointments with South Africa, will replace injured skipper Matt Burke for Falcons' Italian job.
Newcastle rugby director John Fletcher said: "I spoke to Mathew and Brian Ashton about it before making the decision, and they are both very excited about it.
"I don't want to put words into Brian's mouth, but having had a long conversation with him last night about it, he agrees it is a positive move to give him a run at number 15.
"England, in my opinion, have a dearth of quality full-backs, and Mathew has characteristics I feel are very well suited to that role.
"He certainly has a long-term future in the game, but in what position doesn't really concern me.
"Mathew is an outside back, and in my opinion is capable of playing anywhere from 13 outwards.
"I think he will be a sensational full-back, and it was always part of my planning to give him a run there at some point."
Josh Lewsey, Iain Balshaw and Jason Robinson are the perceived principal challengers for full-back duties against England's opening RBS 6 Nations Championship opponents Scotland at Twickenham on February 3.
Ashton though, has a reputation for thinking outside the square, so 20-year-old Tait's switch could conceivably be a sign of things to come.
Fletcher added: "I don't think there is as much room to play at outside centre as there used to be with the way teams defend now, so if you want to bring your strike-runners into the game then full-back is the best place to do it from because of the options and the space you have.
"It is not an experiment, it has been forced on us with Matt Burke being injured, but it has always been in my thoughts, so why not give it a go?
"Whether or not it means he will be a contender for England at full-back isn't something I can say, that's up to Brian.
"But having spoken to him (Ashton) about it, I don't think he is someone who gets too emotional about the number on a player's back.
"You always want your best players on the pitch, and I just don't get away with this thing of pigeon-holing your best players into one position. It's bull."
Ashton is due to announce his team for the Scotland Test on Monday week.