The appointments will be seen as an attempt by the publisher to strengthen the title after it recorded a 1.1% period-on-period increase in sales in the recently published ABCs.
Butt's journalism career has seen her work through a number of UK fashion and lifestyle magazines. She has been features editor at IPC's Loaded and Emap's celebrity bible Heat, and has freelanced for Conde Nast's Glamour and IPC's Marie Claire.
In Style editor Louise Chunn said: "Tammy has had great experience at the coalface of celebrity journalism -- and she is fanatical about glossy fashion magazines. This is the perfect combination for such a critical job in the magazine."
Doe is currently editing the quarterly customer magazine Harvey Nichols Magazine, which is published by Redwood. Her journalism career also includes stints at the Evening Standard and The Guardian.
According to Chunn: "A talented stylist, writer and editor, Tamasin is exactly the kind of multiskilled fashion journalist I wanted to head up the fashion team. She understands that In Style is not like every other fashion magazine -- that it is first and foremost for the reader."
So far this year, IPC has invested £1m in a TV advertising campaign and appointed new editor Chunn to help the title achieve a similar status to its sister title in the US, which is among the top women's glossies.
Both journalists will join the magazine in September.
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