WHATEVER it is, don’t call “Conviction” a “Law & Order” spin-off.

That’s the message from sources close to the new series – even though the show features a former main character from “Law & Order: SVU” and is written and produced by “Law & Order” staffers, including franchise creator Dick Wolf.

It stars, among others, Stephanie March, who will reprise her former “SVU” role as legal- eagle Alexandra Cabot. The assistant district attorney was last seen in and out of witness protection after an attempt on her life a few seasons ago. In real life, the actress is married to New York chef and restaurateur Bobby Flay.

The new show, which began filming this week (ahem, in Astoria, Queens on the former set of “Law & Order: Trial by Jury”) follows “young assistant district attorneys in New York who are confronted with tough, high-profile cases that often challenge their limited experience,” according to NBC press materials. It is scheduled to debut in 2006.

Wolf says the show will be “dealing extensively with characters’ back stories and personal lives.”

But don’t call it “Law & Order: Lost.” That would be bad, too.