Lauri Peterson's son, Josh Waring[1], says an Orange County Jail guard is flat-out lying about Josh's reaction to getting slashed by an inmate ... to cover up a screw-up on the jail's part.

TMZ obtained the criminal report filed for Josh's crazy jailhouse brawl from last month and in it, one of the correctional officers involved claims Josh said right afterward he knew the guards didn't set him up ... or allow the attack to go down on purpose.

Per the deputy's account, he says he asked Josh immediately after breaking up his fight with a razor-wielding prisoner if he knew what happened back there.

According to the report, Josh said, "Oh, I know you guys didn't do that on purpose." Josh also allegedly told the corrections officer he didn't wanna press charges against the slasher. He allegedly explained the guy was in a gang that didn't like him because he's in the protective custody section of the jail.

Josh and his attorney, Joel Garson, are calling BS, telling TMZ ... Josh denies EVER saying anything remotely like that. As for why the guard would fabricate a comment from Josh? Garson calls it a "cover your ass" statement.

When TMZ broke the story of Josh's attack, Garson told us he believes guards showed a blatant disregard[2] for protocol because Josh's attacker shouldn't have been out of his cell at that time.

We know what you're thinking -- there's gotta be video of the guard questioning Josh to clear up the dispute. No dice! The jail tells us their corrections officers don't wear bodycams.

However, Garson tells us he plans to question the deputy under oath during a hearing this week. As we reported, Josh is in the

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