TMZ broke the story … a songwriter named Guy Hobbs sued Sir Elton back in April, claiming Elton jacked his song lyrics … then used them to pen the chart-topping 1985 hit “Nikita” … without Hobbs’ knowledge or consent.

But Elton is firing back — filing his own legal docs in response, claiming, “The suggestion that the Grammy-Award winning composer/lyricist team of Elton John and Bernie Taupin … would need to copy these commonplace elements from [Hobbs’] lyrics is not only baseless and absurd, but it also misses the essential legal point.”

Which is … Hobbs can’t legally copyright an idea — especially not something as broad as a theme involving a Western man falling for a Russian woman.

According to the docs, Hobbs believes Elton also copied his use of the EXTREMELY commonplace phrase “I need you” in the chorus … as well as the words “just” and “never.”

Bottom line — Elton claims Hobbs’ complaint is so vague … the guy has no right to sue for copyright infringement, period.

Elton wants Hobbs’ lawsuit dismissed stat. A judge has yet to rule.