Keith, editor since 2009, has previously edited both the South Wales Echo and the Derby Telegraph. He also had spells as editor and MD of Northcliffe's digital business before becoming MD of the Digital Publishing division of Associated Northcliffe Digital, the combined digital business of the Daily Mail and its regional newspapers.
Perch said: "The past two and a half years have seen unprecedented change in the regional press and, although I have enjoyed every minute of editing the Leicester Mercury, I think now is the right time for me to seek a fresh challenge.
"The team in Leicester is outstanding and I would like to thank them all for their loyalty, support and commitment to the paper."
The newly-appointed publisher at the Leicester Mercury, David Simms, said: "Under Keith's editorship the Mercury has been a vibrant and influential part of Leicester life.
"He has been a passionate ambassador for our business – he's been a positive influence across the region, and proud of the newspapers he's worked on.
"He has recently driven plans for a new Saturday magazine and weekend edition which will launch later this month and we’ve been working together on plans to boost our business coverage.
"We wish him all the best in the future and I’ll be working on the future editorial structure in the weeks ahead."
