"I've been honoured to have led the LTA over the last three years, as we've sought to drive grassroots tennis," Downey said on the LTA's website.
"I am hugely proud of the foundations the team at the LTA have laid in order to turn participation in Britain's beloved sport around ... It's an exciting time for tennis in this country and I look forward to the next six months."
The LTA said it had begin a search for a successor.
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(Reporting by Shravanth Vijayakumar in Bengaluru)
