Don't ever pick a fight with a winemaker. There's nothing someone with a degree in oenology and an ego the size of Sir Richard Branson's dislikes more than criticism. Of course there are modest winemakers, just as there are probably one or two compassionate arms dealers, but these are the rule-proving exceptions. My favourite self-important winemaker story occurred on a trip to Australia a few years ago. The bloke had been banging on about his abilities for half an hour, when he paused for a second. 'Well, mate, that's enough about me. What do you think of my wines?'

My biggest run in with a winemaker took place in New Zealand. The tasting was accompanied by the usual ego brandishing (this many awards, this many press write-ups), but I just ignored it. When I got to the Marlborough Sauvignon Blanc I nearly gagged. 'This is sweet,' I said. 'Bone dry,' came the response. Like characters in a pantomime we argued for a few minutes, with my 'oh yes it is' countered by an equally vigorous 'oh no it isn't'. In the end, I gave up. The next day I bought a bottle and had it analysed at another winery's lab. Guess what? It had nine grams of residual sugar, which effectively made it a medium-dry wine.

I say effectively because a wine with less than 10 grams of sugar can call itself dry. Indeed, in Champagne, a wine labelled as 'Brut' may legally contain up to 15 grams. The point about Champagne - and this goes for other wines with high levels of natural acidity, such as Mosel Riesling Spätlese, Vouvray Demi-Sec and even Marlborough Sauvignon Blanc - is that the sweetness is less obvious because it's balanced by crispness. Or should be. When Champagne is clumsily 'dosaged' it can be truly horrid, with sweetness and sourness wrestling for supremacy.

Our perception of sweetness can be affected by a number of other factors, such as temperature, tannin and carbon dioxide, not to mention alcohol. Wines that are technically dry (under three grams), such as certain New World Chardonnays, will appear sweeter than that because they're what experts call fat (ie lacking in acidity). Nor should it surprise us that alcohol tastes sweet. After all, it's only fermented sugar.

Many wine drinkers are suspicious of sweetness. This is partly because they associate it with cheap German wines like Liebfraumilch, or 'Liberalmich' as my local off-licence manager calls it, and a corresponding lack of sophistication. In their minds, sweetness equals naffness, unless the liquid is a dessert wine.

Their palates don't always agree, however. Most people talk dry but drink sweet, or rather off-dry. Very few wines are bone dry, and those that are can be something of an acquired taste. 'Sharp' is the usual response from consumers, particularly those with a predilection for processed food. That's why most commercial wines contain a few grams of sugar. And it's not only popular branded wines that are getting sweeter. Alsace wines that used to be dry are often medium sweet nowadays.

Creeping levels of residual sugar are mainly found in whites, but can also crop up in reds, especially if they are produced in California or Australia, where a little sweetness is regarded as de rigueur by many winemakers. You can't really blame them, I suppose. Their job is to make wines that sell. And more often than not, leaving a few grams of sugar in the bottle is the easiest way to do it. Just don't argue with them about it, OK?

Six wines to demonstrate sweet and dry

2002 Reuilly, Henri Beurdin (£6.99, Majestic)

A bone-dry, minerally Sauvignon Blanc from the excellent 2002 Loire Valley vintage, this is crisp and chalky with piercing acidity and notes of elderflower and lemon peel. As dry as a dry white can get.

2002 Darting Estate Riesling, Dürkheimer Michelsberg (£5.99, Marks & Spencer)

A wine that carries its 5.5 grams of residual sugar lightly, this is a beautifully balanced, peach and mango-scented Riesling from the Palatinate district, showing the rich fruit flavours for which the area's whites are famous.

2002 Torres Viña Esmeralda (from £5.49, Thresher, Waitrose, Tesco and Oddbins)

This reliable Muscat-based Spanish white has taken two steps forward in the past year: it is now packaged with a screwcap (bravo, Torres) and its sugar level has been dropped slightly from 11 to 9 grams. A spicy, floral, orange zest-scented white.

2001 Domaine Léonce Cuisset, Saussignac (£6.99 per 50cl, Sainsbury's)

You might not be familiar with Saussignac, a sweet wine appellation within the Bergerac region, but it's producing some excellent value stickies at the moment. This toasty, creamy, peach and honey-like white is delicious at the price.

González Byass Noé (£10.69 per half, Tesco)

You want sweet, I'll give you sweet. Some Eisweins and Tokaj Esszencia are sweeter than PX Sherry, but this is still as close to liquid raisins as it gets. Thick, dense and treacly, you could almost eat this with a spoon. Better to pour it over ice cream.

My best buy

2001 Terrunyo Chardonnay, Casablanca (£7.99, Oddbins)

This isn't bone dry, but it's pretty close. It's also an exceptionally good Chilean Chardonnay from the cool, Pacific Ocean-influenced Casablanca region, with mouth-watering acidity, attractive oak and fine, delicate fruit flavours.