Born into a Jewish family in Vienna in August 1908, Edith Suschitzky lived her life in the glare of the 20th century's most turbulent events.

She threw her creative energy into its most vital art form – photography – and in both her life and work she felt the tug of its two defining ideologies, fascism and communism, as well as the various -isms that the Britain she fled to in 1933 held dear before, during and after the Second World War.

But that's only half the story because as well as glare, there is shadow. As Mrs Edith Tudor-Hart, an exile married to well-regarded British doctor Alex Tudor-Hart, she was also a Soviet spy with connections to the so-called Cambridge Ring, whose members included Kim Philby, Guy Burgess, Anthony Blunt and Donald Maclean.

Even her career has its penumbral qualities. It wasn't until the mid-1980s, a decade after her death aged 64, that her work began to be appraised in gallery settings – in large part because its themes of class division chimed with Thatcherism and the miner's strike. And it's only now, 30 years on and in another period of economic slump and social upheaval, that she is receiving her first full retrospective, at the Scottish National Portrait Gallery in Edinburgh.

So where Edith Tudor-Hart is concerned, the gallery's photography curator Duncan Forbes has had to play gumshoe as well as historian. Special Branch files relating to her spying activities were de-classified in 2003 under the 30-year rule and Forbes also gained access to a 160-page report compiled by the Austrian police after she was arrested for her political activities in May 1933. But he knows that information pales beside the archives of the Soviet intelligence service, which remain firmly closed.

And, maddeningly, when Kim Philby was first questioned by MI5 in 1951 on suspicion of being a Soviet spy, Tudor-Hart was worried enough about her own position to destroy a large part of her records. So while her negatives and prints are intact, there is often no way of knowing when or where a photograph was taken.

An example in the Edinburgh show are two images taken on board the vessel Isle Of Arran. One, an angled shot which accentuates the boat's sweeping architecture, shows a uniformed officer starring down at the homburg-wearing passengers with only a life belt revealing the ship's name and its home port, Glasgow. The second shows the passengers themselves: a young woman in a bunnet and tartan skirt, a young man with his arm round her, and a well-fed gent in a three-piece suit looking straight down the lens. Who are they? Where are they going? When? We just don't know.

In fact, it isn't even known when or why Tudor-Hart first picked up a camera, though her early training as a Montessori teacher in Vienna may have had something do to with it. The Montessori method involved close observation of its pupils and cameras were often used to that end. One of Tudor-Hart's earliest assignments as a photo-journalist was for an article about Montessori teaching for a Viennese newspaper.

At this point in her life, the facts do coalesce into something more concrete than conjecture. A dedicated communist, she was in touch with Soviet intelligence by 1926 and was studying photography at the Bauhaus design school by 1930. There she came under the influence of the great Hungarian painter and photographer Laszlo Moholy-Nagy, and under the tutelage of Walter Peterhans, who headed the photography department until 1933.

"Vienna was a very sophisticated centre for photography at that time," says Duncan Forbes. "It had a very prominent art school, but perhaps more significantly it had a very developed studio culture. Viennese Modernism was very strong and photography was an aspect of that. One of the most interesting things is that women – and particularly Jewish women – played a very powerful role in that culture. They were very active in photography."

But as Austria and Germany lurched from one political emergency to another, Tudor-Hart turned from the modernist style championed by Moholy-Nagy to a more vital form of photography: documentary. In particular, she would come to specialise in images of children and women, and of working men such as miners and dockers.

In 1933, she married doctor and political radical Alex Tudor-Hart, whom she had met in Vienna, and the couple moved to London. He took a job as a GP in Wales, but returned to mainland Europe to back the Republican cause in the Spanish Civil War. He and Edith separated shortly after his return.

By now Tudor-Hart was earning her living with photo-journalism. Too authored and stylised to satisfy the demands of Fleet Street, her work found favour with picture editors in the illustrated magazine sector. And so to another date in her life that is indisputable: April 30, 1949. That was the day an issue of Picture Post hit the newsstands containing her pictures of the Camphill School for children with special needs near Aberdeen. The accompanying feature was titled A School Where Love Is A Cure.

Tudor-Hart had more than a professional interest in the Camphill Movement. For a start, it was founded by another Austrian Jewish exile, Karl Konig, whom she may have known in Vienna. Second, her own son Tommy was severely autistic and she had tried unsuccessfully to get him a place there. She visited, publicised the work of the school through her pictures and later gifted a set of images to it.

The journalist who accompanied her there was Edinburgh-born Picture Post staffer (and former Glasgow Herald reporter) Fyfe Robertson, later a fixture on BBC current affairs show Tonight.

"The Picture Post piece is quite romantic in tone and what we've done in the exhibition is only choose one image from the article," says Forbes. "The others are much harder-edged, more interrogative."

The four images in the show, selected from around 50 that Tudor-Hart shot, are among the most powerful in the retrospective – doubly so when you understand the (then radical) theories underpinning the Camphill ethos: that music and touch can be as powerful a medicine as anything taken in capsule form.

The same female teacher features in three images, singing to a group of children, dancing with a young girl or holding the hand of a toddler wearing just a nappy. But it's the arresting fourth image – two troubled-looking boys framed by trees and sunlight – which goes to the heart of what makes Edith Tudor-Hart's work so very special: shooting mostly in medium format with a Rolliflex camera held at waist height, she was able to make exceptionally beautiful images while maintaining eye contact with her subjects. It lends her work a quality of stillness and, at the same time, an extraordinary emotional punch.

"This capacity to make really strong images while retaining a strong sense of realist narrative and engagement is one of the striking things about her," says Forbes. "There is a message in her photographs."

Edith Tudor-Hart: In The Shadow Of Tyranny is at the Scottish National Portrait Gallery, Edinburgh from March 2-May 26, www.nationalgalleries.org