"The Hostage Tower," tonight's CBS movie, plays like retrograde spoof, which means the filmmakers decided it was tongue-in-check after they finished it, and only because it was too ridiculous to be taken seriously.

However, although Keir Dullea doesn't get away with kidnapping the Eiffel Tower, the perpetrators of his just-kidding thriller, at 9 on Channel 9, almost get away with their prank. Certainly the result is moderately entertaining and the cast unusually sparkly for a TV movie.

It includes Peter Fonda, Britt Ekland, Billy Dee Williams and Maud Adams as members of the caper team that the evil mastermind Mr. Smith, played by Dullea, rounds up. Douglas Fairbanks Jr. strolls seedily through the part of an international crime fighter, and Rachel Roberts is his assistant and apparent mistress.

But the spunkiest performance is that of Celia Johnson as the mother of a U.S. president who is captured with the tower and becomes part of a package deal for $30 million ransom. She declares of the mischievous' Mr. Smith, "That is a very silly, greedy man."

As written, the character is too stylish and intelligent to have been consciously fashioned after Mrs. Lillian.

Dullea is first discovered in a hot tub with Ekland plotting the deed, not because he needs the money but because "I am simply addicted to crime!" The years Dullea has spent in England have helped him develop a likable Michael Caine accent, and his smarmy, smirky smile suggests a handsome version of Hugh Hefner.

Robert Carrington wrote the script from a story he co-authored with Alistair MacLean. Director Claudio Guzman inefficiently exploits the Eiffel Tower as a location, and hardly anyone dangles from it in good Hitchcock fashion, although laser beams installed to ward off rescuers are nimble little gizmos indeed.

The musical score by John Scott could be the worst even written for a movie of any kind, but then, there is too much competition for that title to make a final decision possible.