Humphrey Bogart and Ingrid Bergman in the 1942 original

The movie, which regularly tops lists of the greatest films ever made, includes the classic song As Time Goes By and memorable quotes such as: "Here's looking at you, kid", "We'll always have Paris" and "Of all the gin joints in all the towns in all the world she walks into mine".

But one of the lines most closely associated with Casablanca – "Play it again, Sam"– is a misquotation. In fact, Ilsa says: "Play it once, Sam, for old times' sake. Play it, Sam." Later, Rick says: "You played it for her and you can play it for me. If she can stand it, I can. Play it!"

Bollywood filmmaker Rajeev Nath is also said to be working on a remake set in India, calling it "a tribute to the original".

A spokeswoman for Madonna refused to comment.