Fahey, who has a career stretching back almost four decades, first found fame with eighties trio Bananarama.
She co-founded the group with Sara Dallin and Keren Woodward in 1981, co-writing many of the group's biggest hits including Cruel Summer, I Heard a Rumour, Love in the First Degree and Robert De Niro's Waiting.
In 1988, Fahey left the group and founded Shakespears Sister, first as a solo project and later in partnership with Marcella Detroit.
Their 1992 hit Stay, which the duo co-wrote with Dave Stewart, topped the UK charts for eight weeks, the longest running number one by an all-female group in British chart history.
Their Hormonally Yours album released that year went to number three in the UK charts and was certified Double Platinum.
Shakespears Sister and Dave Stewart subsequently received the Ivor Novello Award for Outstanding Contemporary Song Collection in 1993. 1993 also saw The Bluebells' version of 'Young At Heart', co-written by Fahey, re-released and topping the UK charts for four weeks.
Fahey now records music under her own name and writes for other artists.
She said: ‘It's an exciting time for me right now as I'm heading out on tour as part of Bananarama for the first time in 30 years. I'm also continuing to write solo material and work with a great range of other artists. I'm so pleased to start a relationship with Warner/Chappell at this point, as I open the latest chapter of my career.’
Mike Smith, managing director of WCM UK, said: ‘Siobhan is one of the most accomplished female songwriters this country has ever produced. Both Bananarama and Shakespears Sister enjoyed enormous creative and commercial success. We’re delighted to represent Siobhan's incredible catalogue and also look forward to supporting her on new songwriting projects.’
Fahey is pictured above at WCM UK with Smith and Fascination Management’s Peter Loraine.