Phase Eight owner TowerBrook has hired Rothschild to conduct a sale of the womenswear retailer, which is expected to fetch £300m.
US private equity house TowerBrook acquired Phase Eight in 2011 for £80m. It owns about 60% of the business.
Phase Eight generated sales of £141m in the year to February 1. EBITDA was £24m. It is understood it is the best-selling brand in John Lewis, according to The Telegraph.
The retailer operates 400 stores, including 98 overseas.
TowerBrook and Rothschild declined to comment, The Telegraph reported.