Peter O'Donnell, who has died aged 90, chronicled the adventures of his comic-strip heroine Modesty Blaise through more than 10,000 daily appearances in the London Evening Standard, as well as 11 novels and two short-story collections.

The character was inspired by an incident during O'Donnell's second world war service in northern Persia. Camped at a Royal Signal Corps observation post, he and his comrades spied a young girl, obviously a refugee, who eyed them warily but accepted some food. Before she left, O'Donnell gave her two tins of stew and showed her how to use a tin opener. "To this day, I can see in my mind's eye the smile she gave us and the sight of that upright little figure walking like a princess as she moved away from us on those brave, skinny legs," he recalled.

In 1962, O'Donnell was invited by Kennedy Aitken to create a new comic strip for the Daily Express. He was already working on the Daily Mirror's Garth, with its macho hero, and decided to create a female character who was as good at combat as any man, without losing her femininity. His mind went back 20 years to the anonymous urchin. She became the template from which Modesty grew.

A waif herself, Modesty had joined a small criminal gang in Tangiers that she later took over, turning it into an international crime syndicate known as the Network. O'Donnell's first strip related how Modesty, now retired to England after earning a fortune, is approached by British intelligence to help break an organisation known as La Machine. O'Donnell delivered the strip, only to have it rejected by a senior editor at the Express who felt that a heroine who was a criminal (albeit a former one) was not fit for a family newspaper. Charles Wintour, editor of the Evening Standard, had no such qualms. He snapped it up and the strip was an immediate success.

Far from being a wicked, fallen woman, Modesty embodied many strengths. Her loyalty, courage and devotion to her righthand-man, Willie Garvin, translated into any language and their "capers" were syndicated to 40 countries. The writer Kingsley Amis considered the partnership of Modesty and Willie to be one of the greatest in crime fiction, comparable to that of Holmes and Watson.

O'Donnell was born in Lewisham, south-east London, the son of Bernard O'Donnell, a crime reporter on the Empire News. Peter and his brother Roy would sometimes encounter criminals or their girlfriends at the family home, hidden away from rival reporters. One morning it was Harold Davidson, the rector of Stiffkey, Norfolk, whose exploits in "rescuing" prostitutes led to him being defrocked in 1932.

Peter sold his first story, the Lucky Break, at the age of 16 while still at Catford central school. It earned him £4 10s from the Scout. It was quickly followed by sales to the Strand, 20 Story Magazine and others. At 17 he joined the Amalgamated Press, then the largest periodical publisher in the world, where he worked on children's comics, learning the craft of writing scripts and captions in Butterfly, Comic Cuts and Illustrated Chips.

Called up just before the war broke out, he was posted with the Royal Signals first to Northern Ireland and then, in 1941, to the Middle East, later joining the advance through Italy and Greece. He had married Constance Green in November 1940, but did not see her again for four years.

From 1946 to 1951, he worked for a small publishing firm but returned to full-time writing as the paper shortage eased and magazines recovered. Taking an office above the Fleet Street watering hole El Vino's, he churned out three stories and four scripts a week for the Amalgamated Press's comics.

When the author of the Belinda strip in the Daily Mirror fell ill, O'Donnell was suggested as a replacement. Soon he was invited to take over Garth, where he remained for 13 years. He penned strips for the Daily Herald (For Better or Worse), the Daily Sketch (Tug Transom, Eve) and took over the Mirror's Romeo Brown, where he was first teamed with the artist Jim Holdaway ("the greatest of all strip cartoon artists", in O'Donnell's opinion). The two were reunited when Modesty Blaise began her 38-year career in the Evening Standard on 13 May 1963.

Modesty's success attracted the attentions of the film world, but the subsequent pop-art movie in 1966, directed by Joseph Losey, did nothing to capture the qualities of its heroine, portrayed by the Italian actor Monica Vitti. Dirk Bogarde, who co-starred, described it as "a comedy of the absurd gone mad". Only one line of O'Donnell's original script survived – "Have you ever wondered about Mr Fothergill?" – a question later answered by O'Donnell in a two-act play, performed in the provinces as Murder Most Logical in 1974, and subsequently in the West End as Mr Fothergill's Murder.

O'Donnell was, understandably, unimpressed by the experience, but was able to turn his original script into the first Modesty Blaise novels, published by Souvenir Press in hardback and Pan Books in paperback. They remained his publishers for the rest of his career, even when he adopted the guise of Madeleine Brent to write a series of adventurous historical novels.

When Holdaway died suddenly in 1970, he was replaced by Enrique Badia Romero, a Spanish artist who continued the Modesty Blaise strip in the Holdaway tradition for 23 years, with a break between 1978 and 1986 when the strip was handled by John Burns, Pat Wright and Neville Colvin.

Modesty continued to appear in novels, of which Sabre-Tooth (1966), A Taste for Death (1969) and The Impossible Virgin (1971) were the best received, although none failed to entertain. The novels were characterised by O'Donnell's inventive use of bizarre villains, set pieces in which Modesty and Willie were put into situations from which it appeared impossible to escape, and the warm, humorous relationship between the leading characters.

O'Donnell also wrote a popular serial for the BBC, Take a Pair of Private Eyes (1966), and a sequel to the successful movie She, entitled The Vengeance of She (1968), starring Olinka Bérová.

O'Donnell made the decision to retire Modesty in the 1990s and wrote a final selection of short stories, Cobra Trap (1996). The title story relates how the 52-year-old Modesty and Willie, seven years her senior, meet their ultimate fates. He continued to write the daily strip until 11 April 2001, his 81st birthday, and a direct-to-DVD movie, My Name Is Modesty, starring Alexandra Staden, was released in 2003.

In later years O'Donnell suffered from Parkinson's disease. He is survived by Constance and their daughters, Jill and Janet.

• Peter O'Donnell, writer, born 11 April 1920; died 3 May 2010