Newman read English at Cambridge University (Selwyn College). He began his comedy career as an impressionist in the late 1980s before gaining fame when he appeared alongside Baddiel, Hugh Dennis and Steve Punt (among others; this was the regular quartet, however, all of them ex-Cambridge) in the BBC radio and TV programme The Mary Whitehouse Experience (1989-92).

The title was a jibe at the main campaigner for "moral decency" on television, Mary Whitehouse. With The Mary Whitehouse Experience, Newman and Baddiel had become "unlikely pin-ups as, in the early 1990s, comedy was being feted as 'the new rock and roll'," leading to their own series, Newman and Baddiel in Pieces (1993).

The partnership with Baddiel was widely reported as being fraught with tension. Unlike most double acts, their shows (both on TV and stage) were characterised by the two alternately delivering solo monologues, rarely appearing together except in sketches (most famously, History Today). During the "Live and In Pieces" tour, relations deteriorated further, and the Wembley show was widely and accurately predicted to be their last appearance together.

After the break-up, the two men took wildly differing career paths. While Baddiel became part of the new lad phenomenon of the late 1990s, fronting shows like Fantasy Football League, Newman largely disappeared from public life, reappearing with solo work marked by a clear social conscience and anti-establishment views. He covered the anti-globalisation Seattle protests of 1999 for the UK's Channel 4 News. He has been politically active with Reclaim the Streets, the Liverpool Dockers, Indymedia and Peoples' Global Action.

His later work is characterised by a very strong political element, and parallels the work of contemporaries such as Mark Thomas. In 2003 Newman toured with From Caliban to the Taliban, which was released on CD and DVD. In 2005 the show Apocalypso Now or, from P45 to AK47, how to Grow the Economy with the Use of War debuted at the Bongo Club during the 2005 Edinburgh Festival Fringe.

Apocalypso Now toured nationally, sometimes as part of a double-bill where Newman was joined by Mark Thomas. The show was filmed at the Hoxton Hall in Hoxton, east London and shown on More4 under the title A History of Oil, with a later release on CD and DVD. A mixture of stand-up comedy and introductory lecture on geopolitics and peak oil, in Apocalypso Now Newman argues that twentieth-century Western foreign policy, including World War I, should be seen as a continuous struggle by the West to control Middle Eastern oil. A lot of the data on peak oil presented by Newman is taken from Richard Heinberg's book The Party's Over: Oil, War, and the Fate of Industrial Societies.

In 2006 Newman performed a new show, No Planet B or, The History of the World Backwards, at the Tricycle Theatre in Kilburn, north-west London. In 2007, the BBC commissioned a six-part series, The History of the World Backwards based on No Planet B, for transmission on BBC Four. The script of the stage version show is accessible on Newman's official website.