Primark founder Arthur Ryan is to step down as managing director of the fashion retailer in September, when chief operating officer Paul Marchant will become chief executive.

Ryan is expected to stay on as chairman for a period before retiring, according to The Independent.

Marchant joined Primark last year from New Look and was hotly tipped to take over as chief from Ryan, as the 74-year old looks to finally take a back seat in the business he founded in 1969.

Primark, which is owned by Associated British Foods, is also said to have a search out with headhunter Odgers Berndtson for a financial executive. It is not clear if that person would take over from Patrick Prior, the retailer’s current finance director.

Primark is also looking for a trading director after Guy Young, who joined from C&A in 2008, left this month.

In the 16 weeks to June 20 sales at Primark soared 21 per cent. Primark now has 190 stores across 5.7m sq ft of trading space.

Arthur Ryan was ranked 6th in the 2009 Retail Week Power List, published this week. Paul Marchant was listed at number 89.