LONDON, March 31 (Reuters) - Associated British Foods ( ASBFF ) said the boss of its Primark clothing business, Paul Marchant, had resigned with immediate effect following an allegation made by an individual about his behaviour towards her in a social environment.

Primark, the successful fast fashion chain, contributes about half of group profit for AB Foods.

The group said on Monday that Marchant had cooperated with an investigation led by external lawyers, acknowledged his "error of judgement" and accepted that his actions fell below the standards expected by AB Foods.

Eoin Tonge, AB Foods' finance director, will act as Primark chief executive on an interim basis working with the senior Primark management team and Primark's Strategic Advisory Board, while Joana Edwards, AB Foods' financial controller, will act as interim finance director.

AB Foods said Marchant, who had led Primark since 2009, has apologised to the individual concerned, the AB Foods board and also to his Primark colleagues and others connected to the business.

It said the group would continue to offer support to the individual who brought this behaviour to its attention.

"I am immensely disappointed. At ABF, we believe that high standards of integrity are essential," said CEO George Weston.

"Acting responsibly is the only way to build and manage a business over the long term. Colleagues and others must be treated with respect and dignity. Our culture has to be, and is, bigger than any one individual." (Reporting by James Davey; editing by Sarah Young and Kate Holton)