Nina Conti, Soho Theatre

Ventriloquism, once a staple of music hall and variety theatre, has rather gone out of fashion. More mature readers - or students of the form - may be familiar with names such as Edgar Bergen and Charlie McCarthy, Shari Lewis and Lambchop or Ray Alan and Lord Charles, but they are all decades gone from our stages and television screens. Nina Conti is now one of just a few vent acts to have a popular following, and she's reinventing the form.

Her puppets owe more to the soft felt of The Muppets than to the woodworking skills of old, which means her props, while still in many ways caricatures, can appear to have almost human qualities. She fully utilises that in Dolly Mixtures, in which Conti debuts several new characters and in which there's a lively narrative, some breathtakingly brave audience interaction, dark humour and cleverly worked recalls. If I had my doubts about how far she could go with her first puppet, Monk, this show displays not only Conti's astonishing technical skills but also her writerly talents - even if she starts the show by crediting the monkey puppet, with which she has been working for 12 years, as her co-writer.

Monk didn't overstay his welcome, but while he was on stage he declaimed Shakespeare's seven ages of man speech - “Just some shit I wrote when I was locked in a room with a typewriter” - a good joke that formed a sort of skeleton to the show, as we met characters from her life, including Nina, Conti's eight-year-old daughter/her younger self, her much loved Nana and Nana's aged partner, John, who is determined to do away with himself using a motorised piece of garden equipment, plus the comic's fantasy boyfriend, Stefan the builder.

My favourite of these new characters is Killer the pitbull; when we first see him he's seemingly a badly-named sweetheart of a posh pooch in pink who pines for his long-lost brother Joshy, but in reality is a canine who reverts to type if riled. Killer neatly exemplifies the darker nature of ventriloquism, literally an arm's-length guise that affords a comic a means to be kind or cruel, or in Killer's case to turn from dawgy fluff into a hairball of hate in an instant. Killer may be contained by his doggy treats, for which he politely says “thank you” each time, but we soon learn there's a reason why he's a rescue dog.

There are some riffs that Conti has done before, such as Nana's “psychic” shtick with some audience members, but on the whole this show feels fresh and energetic, not least in the potentially unrewarding sections involving the audience, which she handles with great verbal and manual dexterity. When she voices a putative romance between two strangers, on stage and wearing masks - a potential comedy disaster - she turns it into a tour de force of the ventriloquist's form. Add in a level of meta-comedy - as young Nina says, “I don't understand any of my references” - unavailable to a regular stand-up, and this is a rewarding hour of comedy.

• Nina Conti is at Soho Theatre, London W1 until 25 May