THE microwave oven has just been voted the best kitchen invention ever. It's now possible to buy a basic model for pounds-25 or - for more than 10 times that amount - a microwave combined with grill and conventional oven which can roast a chicken or bake a cake, as well as heat up ready meals or defrost frozen mince.

However, despite nutritionists suggesting that microwaving vegetables and fish is as good an option as steaming for retaining all the nutrients, restaurant critics and foodies like to sneer patronisingly when they think they can detect that something has been microwaved. Most recently, the Michelin-starred chef, Raymond Blanc, ranted:

"To put a frozen bag into the microwave for a loved one is an act of hate. Microwaves sterilise completely. It's the most cold act of cooking. When you cook, it should be an act of love."

However, even the most unashamedly practical of British cooks, Delia Smith, has admitted that she occasionally microwaves a ready meal when short of time. So is the magic box that can cook in minutes the answer to our fast-paced lifestyle, our concerns about nutritional values and our need to conserve energy? Or is it increasingly at odds with the return to "real food"? Is there, in short, a place for a microwave in the kitchen of anyone who wants to be healthy?

The first prototype microwave was made in the US in 1947, a year after Dr Percy Spencer discovered that a magnetron tube he was testing during radar research had melted the chocolate bar in his pocket.

When it popped popcorn kernels all over the lab the next day his research took a new turn. In the UK, commercial models first became available in 1958 and the first domestic model was sold in 1974.

Amanda Yates, a cookery writer who has specialised in devising recipes for microwaves since they first appeared on the domestic market, believes they have sometimes been marketed in the wrong way. "In the early days the manufacturers tried to tell consumers that the appliances could do anything and that was a mistake, " she says.

"We would not expect the grill or the hob to do everything."

As a result, she acknowledges that microwave ovens still carry some negative baggage. "The chefs all have them but few admit to using them, " she says.

In her experience, microwaves are particularly good for vegetables, fruit and sauces, especially when cooking small quantities for one or two people.

However, Yates adds that although 90-per cent of households have a microwave, many people still don't use them properly.

"People need to understand that cooking times will vary with the power of the oven and some microwave ovens are too powerful on high for certain things. Just as you would turn the heat down in a conventional oven, so you have to turn down the power in a microwave."

That is as true for the professional cook as the amateur.

Richard Alexander and his wife Moira McFarlane have been forced to learn the tricks of the microwave in order to realise the dream of running their own cafe in Edinburgh. Because it's in a listed building they have been forced to compromise.

"We're only allowed two microwaves and two grills, because otherwise we would need an extractor fan which has to be vented through the roof, but we can't get planning permission for that, " explains Alexander. However, advances in technology mean that Spoon, their cafe in Blackfriars Street, serves a lunchtime menu of soups, fish and extremely sophisticated sandwich fillings.

"The microwaves are invaluable to us, " says Alexander.

"I use them for poaching fish, making confit of duck leg or belly of pork." His microwaves are large, powerful, combination ones with a grill. Like Yates, he is convinced every restaurant has one. "Even Michelin-starred restaurants probably use them for reheating, because it does it much more efficiently than using a saucepan on the stove.

"It's a load of rubbish that it destroys the basic quality of the food. You would not overcook meat under a grill, and you have to be equally sensitive when using a microwave."

That is echoed by Gordon Andrews, who has been involved in developing microwave technology since 1969 and whose company also provides technical training for caterers. "There is criticism of ready meals being junk food and some are, but there are also good products whose nutritional value is well quantified. For example the frozen-food companies are freezing vegetables within a couple of hours of being harvested."

He suggests that poor-quality microwaved dishes result from poor-quality food to start with, or poor technique. "If you look at tests which have found problems with microwaving, you will usually find something abnormal in the testing. A recent Spanish test which compared boiling, steaming and microwaving, boiled and steamed the vegetables in the normal way, but in the microwaving test, covered them with water and used the microwave energy to boil the water, instead of using just one spoonful."

A spokeswoman for the British Nutrition Foundation adds: "We know microwaves are completely safe. A number of studies have shown that no significant nutritional differences exist between foods prepared by conventional and microwave methods."

About 45 million microwave ovens are now sold worldwide every year. As the need to reduce energy consumption becomes more urgent while the number of single-person households continues to increase in the developed world, it is a fair bet that we are going to eat more microwaved meals than ever.

Andrews is upbeat about the future: "Within the next couple of months in this country we will see the introduction of large, multi-shelf, catering models. They will cook better than any conventional oven in terms of texture, quality and weight loss, and will also be energy efficient."

As long as we all calculate the correct cooking time and power.

DOS AND DON'TS DO follow the manufacturer's instructions and be aware of whether your model has a longer or shorter cooking time than average.

DO keep the unit clean. A build-up of grease can affect the efficiency of the oven or even go on fire.

DO be careful when heating food for young children. You could develop "hot spots" in the food that are hard to detect until it is eaten. Stir food well and check it yourself before serving it to a baby.

DO read recipes in advance, particularly if using frozen food, which may need to be thawed.

DO teach children how to use it correctly and that food can heat up some containers.

DON'T heat your baby's bottles in the microwave, as it can leave hot spots in the milk.

DON'T use metal such as cutlery, metal-edged plates, tin foil or even wire twist ties in the oven.

Also watch for hidden bits of metal. The metal can spark - called "arcing" - and both damage the unit and lead to fire.

DON'T cook food in closed containers because pressure can build up and cause an explosion.

DON'T use the microwave if the door seal, hinges, or latch are worn or broken, or if the door has a lot of "play" back and forth.

DON'T use plastic wrappings from bought foods in a microwave oven, as they can melt.