“It should never have happened”

SIMON COWELL has vowed to ensure LEONA LEWIS has maximum security in the future, after a man attacked her at a book signing earlier this week.

The singer hitmaker was signing copies of her new book, Dreams, at a central London store on Wednesday when Peter Kowalczyk allegedly punched her in the face.

Lewis needed medical treatment for a cut across her temple after the incident and she was forced to pull out of a scheduled promotional trip to Germany on Thursday.  Kowalczyk was arrested and subsequently sectioned under the U.K.'s Mental Health Act.

And Cowell, who has guided Lewis' career since she won The X Factor in 2006, is adamant the singer will be better protected in the future.

He tells Britain's Daily Star, "I was stunned anyone would want to attack her. We need to make sure she is protected."

Kris Humphries -- I'd NEVER Sue Kim Kardashian

Kris Humphries has no plans to sue his estranged wife Kim Kardashian over upcoming episodes of "Kourtney & Kim Take New York" ... sources close to Kris tell TMZ.

A report surfaced this week saying Kris was planning on filing a $10 million lawsuit against Kim because of how he expects to be portrayed on the show and because he has a larger role in it than originally planned.

As first reported by Gossip Cop, Kris has no plans to sue Kim. Sources close to Kris tell TMZ he still loves her and their relationship right now is "cordial."

According to our sources, Kris is worried that the show will make him look worse than he really is ... but he understands he has no control of it.