Mr Green says Ms Shepherdson exit is unconnected to Kate Moss

The UK clothing chain, part of the Arcadia Group, confirmed in a statement that Ms Shepherdson had resigned.

Sir Philip Green said the move was unconnected to Topshop's setting up a "design collaboration" with the model.

Denying speculation to the contrary, he said Ms Shepherdson had been fully behind the tie-up with Kate Moss.

'Time for a change'

"Sir Philip and Jane have been in discussions over the past few weeks and as a result Jane has decided that after a long commitment to Topshop it is time for a change," said a Topshop statement.

The firm added that Ms Shepherdson's work on the day-to-day running of the business would be handed over to Karyn Fenn, buying director, and Mary Homer, commercial and merchandising director.

Ms Shepherdson had been with Topshop for 18 years.

She is widely credited with transforming the business in her time at the company, turning it into a firm favourite among young fashion-conscious shoppers.

Topshop said it would continue to explore overseas opportunities while maintaining support for new designers in the UK.