Hoskin told PRWeek he will leave Tesco in mid-October, and a search for his successor is under way.
In his new position, Hoskin will report to Stephen Doherty, MD, head of corporate comms.
Giles Croot oversaw the group media relations remit before he left Barclays in March to join Balfour Beatty, and the role has now been upgraded from director to MD.
Hoskin said: "I’ve learned a massive amount in six years with Tesco but the opportunity to work with Barclays was too good to miss."
Hoskin, formerly head of news at Number 10 during Gordon Brown’s premiership, joined Tesco in 2009 as head of corporate media and became group media relations director in 2013.
Before joining Number 10, he was head of news at the Foreign and Commonwealth Office.