Alzheimer’s-stricken GLEN CAMPBELL – struggling to please fans on his final concert tour – is being mistreated and mocked by some of those closest to him, charge insiders.

The 75-year-old “Rhinestone Cowboy” announced last June that he was suffering from the dread disease and had memory loss problems for years. But now the beloved singer is bravely trying to pay back fans by doing more than 40 farewell concerts in 15 cities.

“Glen does whatever his family wants and keeps saying he’s exhausted, but they just ignore him,” claimed a family friend. “There is no relief in sight.

“Some members of his stage crew – who’ve been with Glen a long time – mock his performance when he forgets something. Their behavior is absolutely disgraceful!”

The friend adds that Glen doesn’t know what city he’s in most of the time, forgets lyrics to songs he’s been playing for 30 years or more and often walks up to the wrong microphone and has to be redirected to center stage. Once, he even readied the band to play “Rhinestone Cowboy” only two songs after he’d got a standing ova­tion for performing the smash hit.

As The ENQUIRER previ­ously reported, Campbell’s oldest daughter and former backup sing­er Debby used to keep him on track, but she was dumped by Glen’s fourth wife Kim Woollen, 54, in a vicious family feud.

Despite it all, the singer of such hits as “Wichita Lineman,” “Gentle on My Mind” and “Galveston” still has “moments of greatness on stage,” said the friend.

“But he leaves many fans feeling pity for him as they watch a legend struggle through the songs he has played flawlessly thousands of times before.”