I saw "Modesty Blaise" in the cinema when it was first released in 1966. At that time I had already read the book, which I loved, and I came away from the cinema thinking that this travesty, this blasphemy of a movie was total trash.
Peter O'Donnell, the author of the book and the comic strip that inspired the movie, went on to write a whole series of books about Modesty Blaise, and I loved them all, especially the first five - six of them, after which the series declined somewhat. I became a greater and greater fan of Modesty Blaise, and my memory of this movie remained completely negative.
Why this negativity? Because the movie does not follow the true concept of Modesty at all. The Modesty books are intelligent and exciting and character-driven, with a touch of humor. In particular, the characters of Modesty Blaise and Willie Garvin (Modesty's loyal side-kick) and their unusual relationship are key factors in the books.
This movie, on the other hand, is just plain silly. It's "campy", with all of the characters acting strangely and with everything that is done being exaggerated. Modesty and Willie, who are both poorly cast relative to their appearance and physique as described in the books, even break into song a couple of times!
So as a movie depicting the "true Modesty Blaise" this movie deserves one star, even though the script does actually follow the first book to a large extent, although everything is modified a bit one way or another.
Now I've watched the movie again on DVD, and my opinion is less harsh.
If you take the point of view that this isn't a Modesty Blaise movie, but a Joseph Losey movie, then it isn't all that bad.