Simon Calver joined Mothercare in April 2012, charged with fixing the group's loss-making UK division. But his efforts to shut underperforming stores and revamp others, grow online and improve products have struggled to make a difference in the face of fierce competition from internet rivals and supermarkets.
The group, which styles itself as Britain's No. 1 retailer of items such as prams, pushchairs and car seats and which makes about 70 percent of sales in the UK, said Calver had resigned as CEO with immediate effect and would leave at the end of March.
It did not give any reason for Calver's departure but added a search had begun for his replacement and that the company's executive management would be responsible for the day-to-day running of the firm in the meantime.
"The board remains confident in the underlying strength of Mothercare and expects results for the year ending March 2014 to be in line with current market forecasts," Mothercare said.
Shares in the firm, which has 231 stores in the UK and around another 1,200 in a better-performing international division, were up 1.7 percent to 251.75 pence at 1248 GMT.
Mothercare had aimed to make a profit on its British operations by 2015, but said in January that 2016 to 2017 was now more realistic.
Last month it warned full-year group profit would reach only half of what analysts had expected, after record Christmas discounting and a drop in visitors to its stores hit sales and margins.
Calver will receive a payment of 250,000 pounds ($417,000)instead of a six months' notice period, Mothercare added.