Fletcher's renown rivalled William Shakespeare's during his lifetime

The National Portrait Gallery in London needs �218,000 to buy the painting, the work of an unidentified artist.

Boosted by a �50,000 grant from the Art Fund charity, the gallery has until 20 January to secure the remainder.

Fletcher was one of the most prolific playwrights of his era, writing three of his plays jointly with Shakespeare.

Two of these survive - The Two Noble Kinsman and Henry VIII - while a third, Cardenio, is now lost.

Fletcher (1579-1625) also collaborated on numerous works with Francis Beaumont, among them The Maid's Tragedy and Philaster, or Love Lies a-Bleeding.

'Delighted'

The National Portrait Gallery's collection of 16th and 17th century poets already includes likenesses of Shakespeare, Ben Jonson and John Donne.

The portrait, which featured in its 2006 exhibition Searching for Shakespeare, will be on display at the venue from 20 November.

Curator Catherine MacLeod said the work would "fill an important gap" in its collection of portraits of Elizabethan and Jacobean writers.

David Barrie, director of The Art Fund, said it was "delighted" its donation had helped the appeal.