Marghanita was born in Manchester, England, to a prominent family of Jewish intellectuals (Neville Laski was her father, Moses Gaster her grandfather and Harold Laski her uncle), she was educated at Lady Barn House School and St Paul's Girls' School in Hammersmith, worked in fashion, then studied English at Somerville College, Oxford She married publisher John Howard (in Paris), and worked in journalism.

Marghanita Laski lived in Hampstead and Abbots Langley.

After her son and daughter were born, Laski began writing in earnest: Marghanita was an omnivorous reader, from 1958 onwards she became a prolific and compulsive contributor to the Oxford English Dictionary and by 1986 had "carded" around 250,000 quotations.

Broadcasting

Laski was a panellist on the popular UK BBC panel show What's My Line? (that ran from 1951 to 1963), The Brains Trust (late 1950s), and Any Questions? (1960s).

An avowed atheist, she was also a keen supporter of the Campaign for Nuclear Disarmament. Her play, The Offshore Island, is about nuclear warfare.

• Love on the Supertax (1944) novel
• Stories of Adventure (1946) (editor?)
• The Patchwork Book (1946) editor
• Victorian Tales for Girls (1947) editor
• Tory Heaven or Thunder on the Right (1948) current affairs
• Little Boy Lost (1949) novel
• Toasted English (1949)
• Mrs Ewing, Mrs Molesworth and Mrs Hodgson Burnett (1950) biography
• The Village (1952) novel
• The Victorian Chaise-Longue (1953) novel
• Apologies (1955) caricature
• The Offshore Island (1959) play
• Ecstasy: a Study of Some Secular and Religious Experiences (1961) psychology
• A Chaplet for Charlotte Yonge (1965) editor with Georgina Battiscombe
• Jane Austen and Her World (1969) literary history
• God and Man (1971) with Metropolitan Anthony of Sourozh religion
• George Eliot and Her World (1973) literary history
• Kipling's English History (1974) Rudyard Kipling poems, editor
• Everyday Ecstasy (1980) psychology
• Ferry, the Jerusalem Cat (1983) story
• From Palm to Pine: Rudyard Kipling Abroad and at Home (1987) biography
• Common Ground: an Anthology (1989) editor
• To Bed with Grand Music (2001) (posthumous)

Persephone Books reprinted The Victorian Chaise-Longue in 1999, Little Boy Lost in 2001, The Village in 2004 and To Bed with Grand Music in 2009.