Top of the Lake: Jane Campion's new scandal melodrama starring the extraordinary Elisabeth Moss

Mad Men star Elisabeth Moss wasn't even the first choice for the lead role in Jane Campion's New Zealand-set mystery series, Top of the Lake, which comes to BBC2 next week. But she's been a revelation, as the director tells Gerard Gilbert

Jane Campion is a surprisingly giggly woman, not at all what you'd expect from the New Zealand film-maker who made that beautifully restrained love story, The Piano, the poetic Bright Star, or the dankly erotic In the Cut. And her first foray into television, Top of the Lake, about the search for a missing 12-year-old girl, has moments of equally unexpected levity. It's slightly more Twin Peaks than The Killing.

"I really love David Lynch," she says. "Blue Velvet made me faint with delight, and Twin Peaks was incredible… so I guess I am an apostle." She even promises a homage to Lynch in one of the later episodes (I have seen the first two), but warns not to take the comparison too far. "I have to be myself even if I am inspired by him".

Top of the Lake, a BBC co-production with Sundance Channel in the States (it's already been shown to great acclaim in America), is set amid the majestic scenery of New Zealand's South Island – the same location where Peter Jackson filmed The Hobbit and Lord of the Rings trilogy. "We came after The Hobbit, and the locals were a bit disappointed because our purse was a lot smaller," laughs Campion.

Her first New Zealand-set drama since The Piano, Top of the Lake has quite a lot in common with the 1993 film. The Piano begins with a woman (played by Holly Hunter) emerging from the crashing waves, while this drama starts with a girl walking into water, seemingly to drown herself. Hunter also co-stars in Top of the Lake, and while she's not quite as mute as her character in The Piano, she does confine herself here to the gnomic utterances that have made her character into something of a guru figure at a refuge for damaged women that is encamped at the eponymous lake.

Meanwhile, the central role in Top of the Lake – that of the policewoman investigating the girl's disappearance – was originally intended for True Blood actor Anna Paquin, who, as a child, played Hunter's daughter in The Piano, winning an Oscar at the age of 11. In the event, Paquin was pregnant, and the role went to Elisabeth Moss from Mad Men. Moss, who "somehow got hold of the script", and asked for an audition. "We were still thinking of English, Australian or New Zealand actors," says Campion. "But when she declared her interest, I thought, 'This can't do us any harm… she's a fantastic actor and I love Mad Menn.'"

In fact, Moss won a Critics' Choice Television Awards for the role last month. "Lizzie was great," says Campion. "She said to me, 'I want to be really pushed in this' and it's really quite nice because it gives you permission to go 'OK, we'll really go for it today'."

Moss is indeed captivating, despite a wandering accent that often sounds more English than Kiwi. Peter Mullan, as Matt Mitcham, the father of the missing girl, is allowed to speak in his native Aberdeenshire voice. "There are a lot of Scottish people in New Zealand," says Campion in defence of this decision. "I didn't feel it was too weird."

Mullan, in a greasy long wig that makes him look like a veteran Hells Angel ("very sexy," reckons Campion), first caught the director's eye in Tyrannosaur, putting in his world-class hard-man act familiar to anyone who saw the recent ITV series The Fear. "I think alpha males are really kind of fascinating," says Campion. "Difficult but also charismatic. Peter talked a lot about the guys he knows from Scotland, his sister works in a high-security jail and he met quite a few of those guys… he felt like he knew the territory."

Equal, in her own sweet way, to Mullan's bad-ass Mitcham is Holly Hunter's "GJ", the leader of a distinctly alternative women's refuge camped in shipping-container homes on the shore of the lake. With "bum-length grey hair", Hunter's character bears a striking physical resemblance to Campion herself. Was this intentional? "A lot of people have commented on that," says Campion with what has quickly become a trademark laugh. "I didn't really see it because Holly's so tiny."

Hunter was at first inclined to turn down the role that would have reunited her with the writer-director who created her Academy Award- winning part in The Piano. "I called Holly up, and I think she was calling back to refuse but I didn't understand," says Campion of a happy confusion. "She got off the phone and told her partner she was doing it and he said, 'What? I thought you were going to refuse?'"

Campion's cinema films have often been described as "novelistic", and although strictly speaking Top of the Lake isn't her first TV drama (her 1990 biography of Janet Frame, An Angel at My Table, was made for television, but exhibited in cinemas), this quality is what attracted her to the small screen. "I was thinking like a novel and I was really inspired by some of the HBO series like Deadwood. Television is actually commissioning amazing material now and in a way it has a more loyal and more interesting audience than film."

Asking about how the plot of Top of the Lake came together elicits a glimpse into her creative process. "One day I was down in this area because I have a hut there," she says, kick-starting a stream of consciousness. "I was starting to feel stimulated by this idea of a mystery story… I went for a walk and saw a container… a burnt-out tree root… organic and tough… and the image of a girl walking into a lake… I don't know where that comes from.

"I also love crime-mystery, and I like scandal as well. We've got the low-brow aspect to it, but I also like investing in it to make it more alive," she says, before light-heartedly summarising the genre to which Top of the Lake belongs. "Yup, it's a sort of scandal melodrama."

'Top of the Lake' begins on 13 July at 9.10pm on BBC2