Is this the new Vettriano?

There are obvious comparison to be made with that other popular Scottish painter, Jack Vettriano, who's Singing Butler recently went for £750,000. However, this makes him unusually testy. He disputes the notion that Vettriano is Scotland's most successful painter since, he points out, his popularity rests largely on reproductions of his art, and the output of original work pales against Morrison's.

The creative frenzy with which Morrison, 58, fills his tranquil Scottish studio is extraordinary to behold. A mountain of oil paint has accumulated next to the easel after years of squeezing out brushes and mixing colours. A pile of squashed-up paint tubes creeps inexorably towards the ceiling.

Morrison claims he is not impressed by Madonna and her ilk. "One of the most satisfying sales I had was to a welder in the village," he recalls. "He hasn't a lot of money and his wife is a nurse in the local hospital. They bought one for £300. He'd saved up for it and they stood all night with a glass of wine, and just admired their painting. Ordinary people doing that is great.

"You can stuff Madonna. I know she didn't even see the paintings before she bought them. She has a curator."

Morrison has many critics among the art cognoscenti but he does have his admirers. Susan Mansfield, art critic of The Scotsman newspaper, says: "He is incredibly prolific, which can work against him, because people think he just churns them out."

"But he has a vigorous use of colour and applies it to the Scottish landscape in an unusual way. This vivid quality is something you might associate with the south of France, but he is expressing something very Scottish."

For more than 30 years Morrison has lived in Argyllshire on Scotland's west coast where he has painted the landscape of the Highlands and islands. Virtually all his works are completed in the studio, and he relies on his sketchbook and his camera.

Despite his speed he says every painting is meticulously researched. More than 30,000 photographs are stored in labelled box files, while guidebooks and hundreds of Ordnance Survey maps fill an enormous bookcase.

"When I go to an area I don't just paint," he says. "I research the history, the folklore, the geology. I study before I paint, and I hope it comes through. I think people unconsciously pick up those vibes. A lot of them say to me, 'There are no figures in your paintings, but I can just imagine a man walking down that road, and someone building a peat stack.' They get right into it. It can be a bit weird."

In the modest modern house adjoining the studio, the artist keeps only 20 of his own paintings. The rest are photographed and the images stored. "So the family will know what I've done in 100 years' time. It's my legacy."

Morrison was born to paint. His grandfather, Henry Lowrie, was an insurance agent but an accomplished amateur water-colourist, and his mother encouraged his interest. At four he had decided he would be an artist and by eight he wanted to attend Glasgow's School of Art. His 1971 degree show was sold out.

It was during a student job in the design studio of a Glasgow carpet factory that he met Maureen.

"Maureen always encouraged me - she saw something that I didn't know I had," he says. After teaching art for more than 20 years, Morrison became a full-time painter a decade ago.

A devout man, he was helping at a Presbyterian prayer meeting when he says he heard God tell him to paint full-time. Within weeks he had given up his job and struck out on his own.

His first solo show at Archway Gallery in the little Argyllshire town of Lochgilphead was a sell-out. He has never looked back.

"I felt that this was what I was supposed to be doing," he says. "I didn't have confidence. It was confidence that something higher than me was in control. He kept me going and still does. I sit at that easel every morning and I think, 'This could go belly up. Don't take anything for granted.'" And what he does with all his money is no less remarkable. "We give away more than we use," he says, apologising for sounding pious.

"We could afford to take a holiday every month, but we don't. We have a boat and a car, but the money goes back to God. You don't just hold on to money, you give back. It's what Maureen and I have always believed."

The couple are patrons of the Princess Royal Trust for Carers and much of Morrison's money goes to charities including Barnados and Save the Children. He has given directly to public-health schemes in Malawi and Zambia. This year his Jolomo Foundation has funded a £30,000 prize for landscape art in Scotland.

"I've not really changed at all," he says. "When I gave up my day job, my heart was in my mouth. But success gives you confidence. Most artists have that sense of uncertainty when they set out. But when you finally see yourself connecting with the world, it's a lovely thing. Hopefully I won't hit a brick wall."

For now that looks very unlikely indeed.

John Lowrie Morrison - A Tour of the Inner Hebrides is at the Air Gallery, 32 Dover Street, W1 (020 7409 1255; www.airgallery.co.uk) 14-20 May.