''Choice paralysis'' was the name given to a peculiar kind of stress felt by shoppers faced with 50 varieties of mayonnaise.

But the wheel is turning. Choices are disappearing as familiar brands are pushed off shelves to make way for products branded with supermarkets' own labels.

In-house brands, such as Woolworths Select, account for as many as one in five goods sold at supermarkets. Estimates vary, but some project they will top 40 per cent within two years.

Food producers say their rise is already restricting choice; data released last week shows Coles' product range contracted 11 per cent between 2010 and 2012.

So what would a home brand supermarket mean for consumers?

For the moment, big savings. Supermarket-branded milk has been selling for $1 for two years, a big-ticket discount in a price war.

Producers have been crying out in pain, saying their margins are being stretched to breaking point. But they warn that once their brands disappear, consumers will be next to suffer.

Also, if Australia's big supermarkets own shelves and the products sitting on them, some competition experts are worried about an unprecedented concentration of power.

You could be forgiven for not noticing the rise of the in-house brand.

Not so long ago ''home brand'' products came in garish packages. The word itself was a slang term denoting something of low quality. That is no longer the case.

The big supermarkets have been expanding their brands to premium ranges, such as Woolworths Select, designed to blur the division between big labels and home brands.

''They've been copying [other brands'] logo colours and fonts,'' says Associate Professor John Dawes of the University of South Australia school of marketing. ''They've been a bit naughty. In any other market the manufacturer would have taken them to court but you can't here. There's only two of them.''

Coles said its in-house brands had a consistent design, making it difficult to mimic individual brands. ''Saying that, cornflakes are cornflakes and they look pretty similar,'' Coles' merchandise director, John Durkan, said.

The supermarkets do not themselves produce the goods sold under their brands. They contract suppliers. Big brand producers can be contracted to make a Coles or Woolworths version of their own product.

Brands are crying foul. They say the rise of in-house brands gives supermarkets the power to demand they lower their prices or risk being moved off the shelves.

The most visible example of this price pressure has been the milk wars.

On Australia Day 2011, Coles slashed the price of its in-house brand milk to $1 a litre. Woolworths immediately followed. Sales of supermarket milk skyrocketed while brand names plummeted.

Coles and Woolworths sell the private label milk at a loss, to bring customers into their stores for other purchases. Dairy farmers say it has the potential to ruin their industry, forcing them to funnel their products into brands with lower margin.

''[We are] a weapon in a war,'' said Mike Logan from the industry group Dairy Connect. ''It brings down the value of the whole product. It puts a ceiling on the growth potential of the industry.''

Coles says it is absorbing the losses on milk itself and that milk prices are determined by international markets.

Producers of other products say they are engaged in an intense competitive war of their own.

They claim to have been subject to ''smash-mouth'' negotiation tactics in which supermarkets demand they lower their prices or simply face being moved off the shelves.

Greenseas tuna and salmon was dropped from Coles in 2011, to the advantage of Coles brand goods.

The Australian confectionary company Allseps said it was dropped after refusing to reduce its prices to the level demanded by Coles.

Brands say supermarkets are decreasing their profit margins and simultaneously competing for their business.

''I feel a little uneasy that a retailer is simultaneously setting the price for its own products and at the same time the price for the manufacturer's product,'' said the former head of the Australian Competition and Consumer Commission Professor Allan Fels.

Coles says that lots of producers have benefited from winning contracts to produce its in-house brands and its competition with Woolworths, but the debate is being dominated by those losing out.

''Many industries had become a little benign here in Australia and they're frankly overpriced,'' Mr Durkan said.

The competition between supermarkets and brands is now naked. Woolworths' advertisements for its Select range emphasise not just its lower price but quality too.

Analysts say that as Australia's big supermarkets bring in more and more of their executive ranks from Britain, where in-house brands dominate, private labels will only grow.

''It's going to have to mean that consumers get less choice,'' Associate Professor Dawes said. ''There's no getting around that. There's not enough space on the shelves.''

Australian supermarkets are catching up to the rest of the world.

Coles says its in-house brands have remained at less than 25 per cent for the past four years. It says it has been pulling its own range and other brands off the shelves in equal measure, because it simply had too many varieties.

Woolworths says in-house brands account for about 11 per cent of products. In 2011, the supermarket said it aimed to double their sales.

In Britain, such brands make up nearly half of all packaged goods.

In America, the in-house brand has taken on a kind of cachet. Consumers flock to stores such as Whole Foods because of the quality of their brands.

Steve Ogden-Barnes, a retail industry fellow at Deakin University, says that while some British brands have lost out, in-house labels have been beneficial for consumers and retailers.

But Australia's supermarket industry is more concentrated. Coles and Woolworths take in up to 80 per cent of money spent in the grocery market.

''Retailers are in the profit game,'' Dr Ogden-Barnes said. ''They will charge the highest price they can whilst being perceived as remaining competitive.

''As choice goes down, then yes you do have more control over the price landscape.

''As you see more [supermarket brands] on the shelf you might expect to see some upward movement in prices but the great leveller will be what the competitors are doing.''

The food industry says as its brands disappear, supermarkets will have an essentially free hand and steep discounts will be overturned.

''This is a classic Trojan horse tactic,'' the chief executive of the Food and Grocery Council, Gary Dawson, said. ''As the range of choices drops, so does competition, raising the risk in the longer run supermarkets will have more market power to increase prices at will.''

Coles says that Australia's retail market is actually becoming more competitive, especially as Aldi increases its business.

It says its prices have deflated by about 3 per cent over the past four years.

''Prices are going to become lower not higher,'' Mr Dawson said.

Professor Fels agrees that competition has stiffened recently - something he attributes to Coles pulling up its socks to regain lost market share.

''I can imagine a time before long when the two main players decide that enough is enough and they won't compete so hard,'' he said. ''There's no real insurance that it will continue indefinitely.''

That risk, he says, is inherent to Australia's concentrated retail market and will determine how much benefit consumers reap from the rise of in-house products.

''In Australia the chances of there being a consumer benefit are greatly reduced,'' he said.

''In a few years with such a concentrated market we may have real concerns about market power and [supermarket] labels.''

Just how far private labels rise in Australia - and how much power supermarkets acquire - will depend in part on whether consumers can forget their past association with lower quality. But their share of some products, such as butter, is already close to 70 per cent, according to IBIS World.

Professor David Hughes from the Imperial College in London, says attempts by some supermarkets in Britain to lift levels of in-house brands above 50 per cent met with a consumer backlash.

Why? Because people are still attached to labels - and to choice.

How true this is of Australian shoppers remains to be seen.