Ray J says he’s ready to bring out a major witness in his ongoing war with Kim Kardashian and Kris Jenner over the infamous sex tape … and it’s someone who he claims would know exactly what went down.

The singer’s lawyer, Howard King, tells TMZ … if Kim or Kris continue denying they worked with Vivid Entertainment boss Steve Hirsch to release the tape, King’s team is prepared to call Hirsch himself to testify.

TMZ broke the story … both Kim and Kris filed sworn declarations this week saying they did not mastermind a plan to shoot, sell and release the tape, “Kim Kardashian Superstar.”

Those statements were made under oath, King claims the mother-daughter duo flat-out lied.

Quick reality check, and we’ve reported this for years now … there’s no legal way Vivid could have released the sex tape without Ray and Kim signing off on it, so that part’s not really in dispute. The debate now is really about how involved Kim, and particularly Kris, were in making the deal.

In her declaration this week, Kris said it’s “absolutely false” if Ray J, or anyone else, claims she was involved in the “commercial exploitation” of her daughter through the sex tape.

In old interviews, Hirsch — who no longer owns Vivid — has said Kris had no role in selling the tape.

As you know … Kim and Kris filed a lawsuit against Ray J back in October, accusing him of defamation — and he fired right back with a countersuit, claiming they broke a settlement agreement that bars anyone involved from talking publicly about the sex tape.