LONDON, April 27 (Reuters) - **Marks & Spencer shares fall 5%, Primark owner Associated British Foods ABF.L falls 1.2%
** JPMorgan says Worldpanel data for the 12 weeks to 29 Mar shows "a material slowdown in the UK clothing market to -3.8% year-on-year vs -1% in the 12 weeks to 1 Mar"
** JPM says data shows Marks & Spencer decelerated to -0.5% year on year compared to a 3.2% increase for the previous 12 weeks. They say this echoes their analysis of online web and app traffic that pointed to a slowdown in March and April.
** Marks & Spencer does not immediately respond to emailed request for comment
** JPM says as ABF updated the market last week, there is little that is new for them in the data
(Reporting by Alun John; Editing by Amanda Cooper)
((alun.john@thomsonreuters.com;))