His departure follows a profit warning in August when the firm said sales have been hit by the number of customers holding onto their handsets for longer as rising inflation and stagnant wage growth weighs on disposable incomes.
It has been an enormous privilege to lead this business and to work with such passionate and committed colleagues over the last few years.
Shares in Dixons Carphone, down 45 percent year-on-year after an August profit warning, were up 2.4 percent at 0950 GMT.
'Although the weaker trend in United Kingdom electricals after Boxing Day was disappointing, overall trading was solid and consensus FY18 forecasts are unchanged, ' commented analysts at Numis Securities today.
The group narrowed its expected full-year headline profit figure to a range of £365m to £385m, having previously pencilled in £360m-£400m.
A close friend of former prime minister David Cameron, Mr James emerged past year as a contender to run commercial broadcaster ITV, but the role eventually went to Carolyn McCall, the then easyJet boss. In UK & Ireland electricals, our Boxing Day sales did not quite mirror the promise of our very strong Black Friday week, but we are very confident that we grew market share in pretty much every category.
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Its Greek and Nordic markets were the stars of its Christmas trading update, recording a significant like-for-like revenue increases of 23 per cent and 11 per cent respectively.
Mr James said that in United Kingdom and Ireland "our Boxing Day did not quite mirror the promise of our very strong Black Friday week, but we are very confident that we grew market share in pretty much every category".
The company expects net debt to reduce to about £250mln by the year end and cash outflow for the year is estimated to reach £50mln, compared to a previous forecast of £40mln. Going forward, it hopes to benefit from an early Easter, the launch of a new Samsung phone, and the first two weeks of its World Cup promotion.
Store closures on the horizon?
However, Mr James said there were some bright spots ahead.
But Mr James said market conditions meant that its profit margins in the mobile phone business "continue to be challenged".