Frank Cohen started out in the painting and decorating business 50 years ago. But despite making a fortune from DIY, it is a different kind of painting for which he is most now famous.

Cohen, 65, is one of the best-known collectors of contemporary art in the world, with a collection worth millions amassed over 40 years. He is known as the “Saatchi of the North”, after that other famous Jewish art lover, and in reference to the fact that he has resisted the lure of London — the centre of the art world — and is still based in his hometown of Manchester.

Having left school at 15 to work on market stalls selling paint and wall coverings, Cohen went on to make a fortune by founding the Glyn Webb DIY stores. He sold up in the late 1990s to concentrate on art. In 2007 he opened his own exhibition space, Initial Access, on an industrial estate in Wolverhampton (chosen because it is half-way between London and Manchester), where selections from his collection are regularly on show.

Three years ago, he exhibited part of his collection in London for the first time, only to receive some scathing reviews from critics. He is now trying again, this time at the prestigious the Royal Academy.

Cohen was born in the Cheetham Hill region of Manchester in 1943; a time, he recalls, when the area was “a Jewish ghetto”. His grandparents were immigrants from Russia, but his parents were born in Manchester. He caught the collecting bug when he was a young boy. But at that time it was less about fine art and more marbles and cigarette cards.

“As a boy I collected anything that was limited in edition or interesting. Then I got into coins. I had at one point the largest collection of rare coins in the UK. My wife Cherryl’s father, Jack Garson, a very well known character in Manchester, collected British art and antiques. When I went to pick up my future wife one day from their home, I bought an LS Lowry-signed limited edition print from him. Several visits later and I’d built up quite a collection.”

Soon, he had built up a large number of Lowrys and other modern pieces by British artists. “When I saw the Freeze exhibition in 1988, curated by Damien Hirst, I developed a real passion for contemporary art and since then it’s just grown and grown,” he says. “Now I buy work that I love, but also always have in mind the fact that I have an exhibition space that is open to the public, and so I have a responsibility to develop themes and ideas through my collecting that make sense in the context of a contemporary art gallery.”

The complete collection now comprises some 1,500 pieces. But, Cohen claims that each one has been carefully selected. “I think first about my immediate, emotional or aesthetic response to the piece, then about whether it might fit into an exhibition or even whether it might be so radically different that we could show it off with something completely opposite.”

In an ideal world he would love to purchase a Picasso, a Rothko or a Pollock, but even millionaire collectors have their limits. Not that he is forthcoming about what he is prepared to pay for any given piece, only being prepared to say: “I spend what I feel is right.”

Cohen is one of a select band of wealthy Jewish private collectors which includes Charles Saatchi and Anita Zabludowicz.

“Charles is a friend of mine and we speak regularly about our collections,” he says. “I can’t really say whether being Jewish has anything to do with what you do in contemporary art, although I think that there is a rich Jewish tradition of collecting art, so I’m pleased that it seems to be continuing.

“Equally, though, my passion for collecting is borne out of a number of different factors: my interest in global developments, my appreciation of emerging talent, my love of visual things and my desire to show what I have to as many people as possible.”

Although the collection is diverse , there are recurring themes — destruction and death being two of the most noticeable. Cohen believes geography plays a part.

“I think this comes from the fact that many artists whose work I’ve been collecting, particularly from Korea or China recently, focus on the issues and themes that affect their lives and their respective histories. It’s therefore not a great coincidence that some of the themes among artists from the same place or time come together, either in form or thought. There are a number of strong themes in my collection but, as I’ve said before, I buy work that I love.”

The modern trend for private collectors to hoover up artworks that might formerly have ended up in a public gallery or museum has not pleased everyone. However, Andrew Renton, the director of curating at London’s Goldsmiths College and a former Turner Prize judge, sees Cohen’s role as fundamentally positive.

“What he has done is symptomatic of the way art has gone in the past five years — namely dynamic, aggressive collecting by private collectors,” he says. “It is easy to criticise collections like his but more interesting is to understand what they can do. They provide a wake-up call to public collections. They can operate at a pace that public collections cannot keep up with and they have budgets that public collections cannot match.”

Renton adds that private collectors such as Cohen have an inbuilt advantage when bidding for works. “These collections fill a gap. Museums have to tread carefully, they have to have a sense of the bigger historical perspective. Private collections such as Frank’s are important because they are personal, irresponsible, dynamic responses to what is going on in contemporary art.”

Jeremy Lewison, former director of collections at the Tate Gallery, agrees that private collectors fulfil a different function to that of museums, and as such should not come into conflict with the great institutions.

“I think collectors like Saatchi and Cohen can react more quickly to contemporary developments. They don’t take as long to sift through work by different artists. Museums, on the other hand, have smaller budgets and buy fewer pieces, so they have to be more selective.

“These collectors have their place but they can’t replace museums. Artists still value public collections because they know their work will be preserved permanently.”

And he has reservations about the way some collectors can influence artistic careers. “I don’t know about Frank Cohen, and Anita Zabludowicz is not the sort of person to throw her weight around, but Saatchi can make and break careers and has done so.”

Cohen himself is in no doubt about why he collects and displays. He buys, he says, because he loves art, and never because he considers a work to be a good investment. And why does he mount exhibitions? “Because I don’t see the point in collecting things and keeping them in storage. I want, like all collectors who own public spaces, to make something out of it and keep the work alive through the people that get to see it.”

Dark Materials, an exhibition of works from the Frank Cohen Collection, part of the GSK contemporary season, is at the Royal Academy, London W1 from December 13-January 19. Details at www.royalacademy.org.uk. Information on exhibitions at Initial Access is available at www.initialaccess.co.uk