The world number four was labelled a "drama queen" by former Wimbledon champion Virginia Wade after he required on-court treatment on his troublesome disc during his second-round match against Jarkko Nieminen at Roland Garros last month.
Murray has responded by clarifying the extremes he had to go to just to participate in Paris.
Quoted in several newspapers, the 25-year-old said: "I think eight painkilling injections in your back before the French Open justifies a genuine injury.
"If someone is going to say to me my back injury is not genuine, they can come see my reports from the doctors, they can see the pictures of a needle about eight inches long in my back.
"I'm not accepting criticism any more because it's not fair."
American John McEnroe, winner of nine grand slam singles titles and now a television commentator, has also questioned the severity of Murray's problem, claiming it could be a "mental thing".
The British number one added: "A lot of people have suggested that it hasn't been genuine. But it's certainly not a mental thing.
"Often when things do start to get better. For a little while you can be over-sensitive in that area and think, 'Oh, is that not right?' But with my back problem, it's something that's there."
Murray has been handed a tough draw at Wimbledon as he chases a first major crown, beginning his 2012 campaign against Russia's former world number three Nikolay Davydenko in the first round on Tuesday.