UPDATE 1-WPP could publish findings of CEO investigation next week - source

(Adds background, details)

LONDON, April 9 (Reuters) - WPP could publish the findings of its investigation into an allegation of misconduct against Chief Executive Martin Sorrell as early as next week, a person familiar with the situation said.

The world's biggest advertising group sent shockwaves through the industry last week when it said it was investigating an allegation of misconduct against Sorrell, raising the prospect that the founder of the British company could step down after more than 30 years in charge.

The 73-year-old Sorrell has said the allegation regards the use of company funds and that he rejects any wrongdoing "unreservedly". In a statement he has also said his commitment to the group remains absolute.

"It won't be this week, it could be as soon as next," the person said, speaking on condition of anonymity due to the sensitivity of the situation. WPP declined to comment.

The longest-serving CEO on the FTSE 100 blue chip index, Sorrell built WPP into the world's biggest advertising group by three decades of relentless dealmaking.

In his time the group has expanded to own top creative agencies including J. Walter Thompson and Young & Rubicam, as well as media planners and buyers and market-research and public-relations groups such as Finsbury.

Present in 112 countries and employing more than 200,000 people, WPP provides services to clients including Ford, Unilever, P&G and a string of major corporations. It has been hit in the last 18 months by a downturn in consumer spending and rapid technological change. (Reporting by Kate Holton; editing by Guy Faulconbridge)