Duncumb will leave having been a major driving force behind the business. Duncumb was responsible for developing the Lepel lingerie brand and completing the acquisition of the Charnos business in 2006.
Duncumb will continue to work in the business for the next couple of months to handover responsibilities to her team. Non-executive director Peter Newbold is also stepping down from the board after 22 years at the group.
In a statement Initmas chairman John Gibson said that he would take on the role of executive chairman on a temporary basis. He said: "We are actively reviewing the composition of the board, but anticipate the recruitment of at least two new non-executive directors."
The announcement comes following a strategic review of the business over the past two months. Sales at Intimas fell 8% to £19.5 million for the year to December 3, with the company reporting a loss before tax of £3.6m compared to a profit of £1.07m the previous year.
Gibson said that as a result, Intimas will also relocate its Charnos lingerie operation to the Initmas group head office in Long Eaton by August. Gibson also added that central overhead costs will be "rigorously controlled".
The company will also discontinue its retail roll-out plans.
Gibson said: "Our high street stores have been performing significantly below initial expectations and there will be no further roll-out in the foreseeable future. We believe that both our brands and private label businesses are capable of delivering significant growth over the next three years."
The business said it was making progress in terms of stock clearance but added that no further expansion of the brand's factory outlets is envisaged.
"Performance for the first four months of the financial year is ahead of last year and in line with expectations," he said. "As widely reported, high street retailers and the clothing sector in particular are suffering a significant downturn and we continue to view the outlook for the remainder of the year as challenging. Nevertheless, we do anticipate a significantly better first half and full year performance than in 2007."