Yesterday the Spice Girls launched their second album on a tidal wave of hype. The album, their movie and their merchandising deals should make them rich. But Paul McCann has found evidence that their ludicrously young fans and the endless exploitation of the band's name signals the beginning of the end for the Spice phenomenon.

The writing is on the wall for the Spice Girls. OK, they celebrated the launch of Spiceworld by flying journalists to Spain to guarantee plenty of publicity and it still looks very much as if the world is subject to Girl Power.

A Spice Girls' movie is due out before Christmas. Walkers have sold 16 million packs of their Spice Girls crisps. Pepsi is receiving 12,000 applications a day for a Spice Girls single that can only be heard by buying a can of Pepsi, and Asda has signed them up to a pounds 1m deal to put their name on 40 exclusive "Spice" products from food to stationery.

But those who know about these things know they probably won't last far into next year. That comes from no less an authority than than Alice Moore, a nine-year-old from Stroud in Gloucestershire, and Marketing Week, the esteemed business magazine, who both believe their days are numbered.

When she was eight Alice was in mourning when she thought the Spice Girls were splitting up. Now she is nine she has declared she is "too old" for the Spice Girls.

One of the reasons may be because four-year-olds like Daisy Fox, also from Stroud, are now the band's biggest fan: "They are shiny and pretty and bright," says Daisy's mother Emma Ray. "And so they're perfect for little girls. The songs have a simple, nursery-rhyme quality and there is one for every taste. At the moment Baby Spice is the favourite because she has fluffy hair."

A four-year-olds' obsession with a pop group might seem odd to adults who think pop bands are for the teenage years, but it makes perfect sense to Ms Ray: "It provides kids with security if they are familiar with something that everyone else knows about. It makes them feel part of something."

The popularity of the Spice Girls by such young children is not unprecedented. "This is a familiar pattern of take-up," says Melvyn Thomas, managing director of merchandising agents The Licensing Company. "Part of the appeal of pop groups or movies is aspirational. It starts off with the 11-, 12- and 13-year-olds, and then their younger siblings and friends want to emulate them and get involved."

The problem is that the older fans will drop a band or movie when the younger children get on board because it is no longer "cool".

This could explain what Marketing Week describes as the "overkill" of Spice Girls deals. On top of the products already mentioned there is also an Impulse Spice range of scents, a tie-up with Chupa Chups lollipops, a Polaroid SpiceCam and a BT advertising campaign planned before Christmas.

Spice trademarks have been registered across everything from arcade games, cars and even weather vanes, indicating just how much the group's management plans to screw out of their popularity.

"Daisy seems to believe they are a brand name that can feasibly appear on anything that she might want," says Emma Ray. "She will go for the Walkers Spice Girls crisps even although she prefers another flavour. She wants Spice Girls yoghurt, even although it doesn't exist."

Ms Ray believes that the sheer quantity of Spice Girl products has strengthened the Spice Girls' popularity by making them a ubiquitous part of her little girl's life. Marketing industry experts believe companies are getting involved because that very ubiquity could mark the beginning of the end for the band's popularity - and they don't want to be left with warehouses full of Spice merchandise if the bubble bursts.

"It is impossible to put a date on when they will kill the goose that lays the golden eggs," says Melvyn Thomas. "It becomes a self-fulfilling thing if more and more people pile in to do deals worried that they may leave it too late. A shortage of goods sustains a craze, but if it is everywhere, it stops being cool."

People in marketing talk about "playground currency". Trends and crazes sweep through children with an intensity that can make a toy, lunchbox or sticker manufacturer sing in the bath. For the next three months it will indeed look like we live in a Spiceworld.

But unless the Spice Girls' appeal now moves from four-year-olds to toddlers they will be making way for the next big thing. The toddlers' marketing gap has already been filled: Daisy's little brother Jake is mad about the Teletubbies.

Cash power The deals so far:

Pepsi: rumoured pounds 1m deal that gave fans access to a single only through buying cans of Pepsi. Pepsi drinkers can get the first tickets to their live concert in Turkey next year.

Asda: believed to have paid pounds 1m to be able to produce 40 "Spice" products in its 214 stores - from a Scary Spice Pizza to Christmas crackers.

Chupa Chups: no product is too ludicrously named for the Spice Girls to endorse and they dutifully adopted their "Girl Power"-point-at-the-camera pose for these lollipops.

Polaroid: A new range of cameras, the SpiceCam, which can be customised with stickers of each Spice Girl, will be launched before Christmas.

Elida Faberge: Unilever's cosmetics subsidiary is actually launching a new range of Impulse scents - which are aimed at young teenagers - with a scent that is to represent each member of the Spice Girls.

Cadbury: The girls will be the inspiration for a new product line. They are not just endorsing products. They are inspiring their creation.