The Lives of Others was such a brilliant achievement that it is hard to believe that writer/director Florian Henckel von Donnersmarck could make a misfire as dire as The Tourist. The involvement of Julian Fellowes in the screenplay makes it seem even more of a bizarre failure.

A romantic thriller-cum-comedy, it stars Angelina Jolie and Johnny Depp, flanked by the likes of Paul Bettany, Timothy Dalton and Rufus Sewell (Jolie is the only female character).

Depp plays Frank, ostensibly a teacher from Wisconsin taking a European vacation. Jolie plays Elise, a mysterious, stunningly glamourous, constantly overdressed Englishwoman (yes, Jolie reprises her excellent English accent from Lara Croft: Tomb Raider) who picks up Frank on a train in France and entices him into accompanying her to Venice. Once there, she puts him up in her suite at the sumptuous Danieli hotel.

It seems that Elise is in town because she has been summoned to meet her lover, Pierce, who disappeared after stealing a fortune from an international gangster named Shaw (Steven Berkoff, deftly drawing on countless similar villains he has played before).

It also turns out that various people are watching Elise and Frank with malign intent. They include Italian agents of a ruthless British policeman (Bettany) and Shaw's shaven-headed Russian henchmen. Both agents and gangsters believe that Frank is in fact Pierce - and it soon becomes clear that Elise picked him up so he could serve as a decoy.

This puts him in peril as the Russians - the criminal equivalents of Keystone Cops - chase him in his pyjamas over the city rooftops. The sequence is neither that exciting nor funny, though the over-the-top score pretends that it is both.

There are jokes scattered between the boat chases down the Grand Canal and the generally feeble gags are clearly intended to impart an archly comic tone to the whole proceedings.

Indeed, the film is an attempted homage to, or update of, that genre of romance-comedy-thriller exemplified by Stanley Donen's 1963 Charade, which was set in Paris and starred Cary Grant and Audrey Hepburn. The Tourist works particularly hard to evoke Charade. At times it even seems as if Jolie has been costumed and made up to recall Hepburn - she is all huge eyes and cheekbones above narrow shoulders and a sylph-like silhouette, on which is draped one couture frock after another.

As Frank, the tourist drawn into a world of black-tie balls and implausible international intrigue, Depp is supposed to be handsome, coolly unflappable and naturally elegant in a way that recalls Grant. It is disastrous casting, not just because Depp is too short and boyish looking, but because Jolie's presence is so overwhelming that you never believe that her character and his belong in the same romantic league. And one of the key elements in films like Charade is that both leads must be equally attractive.

You get a sense that The Tourist must have been much more fun to make than it is to watch. Nevertheless, Donnersmarck films it like an advertisement by the Venice tourist board, and compared to Venice-set movies like Don't Look Now or Death in Venice, The Tourist's failure to make effective use of the city's moods is remarkably uninspired.

Instead, it feels like a crass exercise in luxury porn. Certainly there is something obscene about the way Donnersmarck captures Jolie's and Depp's arrival at the Danieli hotel and then gawps at the decor of their palatial suite.

But the worst thing is that the film is so unexciting that it is hard to suspend disbelief and get into the story. Instead, you find your attention wandering to extraneous matters - such as how Jolie's excessive thinness has made her extraordinary features look like the results of plastic surgery.