James began dating the former model and actress after meeting through their mutual friend, Princess Eugenie, in 2013.
Rumours recently surfaced alleging the couple had called it quits, but Middleton and Air have now addressed the speculation by releasing a joint statement to British newspaper The Mail on Sunday.
"Mark Twain once complained that reports of his death were exaggerated," they wrote. "A few days ago we were equally amazed to read the obituaries of our relationship splashed across the national press.
"Happily, we can report that our relationship is not over. We are still very much a couple and have not parted ways. These stories are completely untrue and without merit."
The couple was last pictured together at the Wimbledon tennish championships in London in July (15).