It's time for Scots to turn down the heat '¨and step away from their microwaves...

They are the time-saving gadgets which have divided opinion since they first came on the market in the 1960s.

Now a Scottish chef has taken criticism of microwave ovens further by describing them as “the worst invention ever”.

Graham Campbell, who in 2009, aged just 29, became the youngest chef in Scotland to win a Michelin star when he won the accolade for Ballachulish House near Fort William, said microwave cooking was contributing to the nation’s obesity crisis as people were too busy to prepare fresh food for themselves.

Campbell, 36, who now runs the award-winning Castlehill restaurant in Dundee, and appears in The Final Table, a multimillion pound cookery show on Netflix this week, is calling on people to unplug their microwaves and invest in a slow cooker instead.

“The world is too fast and no-one has time to cook healthy food any more,” he said.

“The microwave oven is the worst invention ever. You never see adverts for the slow cooker, which is a shame because I think there should be one in every home.

“Bung in your ingredients – vegetables, meat, stock – and you have a healthy meal by the time you get home: job done. Far better than ready meals that are full of s***.”

Oban-born Campbell who had previously appeared on the BBC’s Great British Menu, was selected from hundreds of chefs to appear to the ten-episode television features 24 world-class chefs competing against each other, cooking iconic dishes from different countries.

Slow cookers, known as “crock-pots” in the US, allow lengthy “hands-off” cookery where a dish such as a stew can be left to cook for about ten hours overnight or when out at work.

They are not to be confused with pressure cookers which use super-heated steam where meals can be made in under an hour.

Nick Nairn, the Scottish celebrity chef, author and columnist who received an honorary doctorate from the University of Stirling in 2007 for his contribution to Scottish cooking and healthy eating, said he agreed with Campbell about ditching ready meals but said the obesity crisis involved many complex strands, some political and some socioeconomical.

Nairn, 59, who in 1991 was the youngest Scot to win a Michelin star when he won the award for Braeval, the restaurant he set up near Aberfoyle, said: “Slow cookers have fallen out of fashion and are overdue a revival. The problem is that on television they will be seen in an out-of-the-way shot because they’re not very sexy.

“Telly cooking is all about bish-bash-bosh, not about slow cookers.

“But they are great for making healthy, nutritious meals, and great for cheap cuts of meat such as pig’s cheek and lamb neck. The cost of home-produced food is a fraction of anything you would get in a restaurant.

“I’ve been banging on about the obesity crisis for 30 years and it’s incredibly complex. We as a nation and the government don’t take food seriously enough. Politicians seem to forget it is the biggest lobby in the country.

“In general, if you can’t cook you are disempowered. You’re handing your diet to someone else and you don’t know what’s in the meals you buy. Learning to cook is an essential life skill so people can feed themselves.”