A peculiar and tiresome piece of cine-narcissism here from Christophe Honoré, based on an insufferably twee kind of cinephilia – yet rescued, slightly, by the down-to-earth drollery of Catherine Deneuve, who is playing herself.

Chiara Mastroianni, the Franco-Italian actor and Deneuve’s daughter, is of course very well known for her startling likeness to her father: the film icon Marcello Mastroianni. We see her here also playing herself and acting in what is evidently supposed to be a homage to Anita Ekberg’s Trevi fountain scene from Fellini’s La Dolce Vita, in which Marcello famously starred. She feels haunted by her father and has a dream in which her face turns into Marcello’s in the bathroom mirror; actually, it is not much of a change. She confesses how unhappy she is about her “Marcello” face to her mother, Deneuve, who reassuringly says that, yes, Chiara has his expressions but not his face. (I wonder if Deneuve actually believes that in real life?)

Then Chiara plays a scene for sharp-tongued director Nicole Garcia (again, playing herself) who tells her she wants her to play it Marcello, not Catherine. Something in Chiara snaps, and she starts dressing like Marcello all the time, in the black suit, glasses and hat that Marcello wore in Fellini’s 8 1/2. She requires her friends to call her “Marcello” and not to deadname her “Chiara”. Fabrice Luchini plays himself becoming the best pal of “Marcello”, although Luchini’s natural performing shrewdness would be better suited to a sceptical role. Melvil Poupaud is furious about this new identity. It all ends in crisis with this new “Marcello” appearing on a TV talkshow dressed like Marcello from Fellini’s late movie Ginger and Fred.

There is a persistent strain of pointless, time-wasting silliness to this film. Whatever feelings Chiara Mastroianni really has about resembling her father, and whatever her actual feelings about this possibly oppressive inheritance, they are clearly not going to be revealed in this all-but-unbearable, precious piece of whimsy. It’s an indulgent doodle of a film, a self-admiring industry in-joke, an earthbound flight of fancy, unconvincing on a literal level, and unenlightening on a metaphorical level. Yet Deneuve, puncturing her daughter’s affectations and delusions with a wry and bemused smile, injects some real humour.

• Marcello Mio screened at the Cannes film festival.