LONDON, April 27 (Reuters) - Vodafone confirmed interim chief executive officer Margherita Della Valle to the role on Thursday, saying she impressed the company's board with her "pace and decisiveness to begin the necessary transformation" of the mobile operator.

The British company said it had conducted a rigorous internal and external search before choosing the insider, who has been chief financial officer since 2018.

She stepped into the top role on an interim basis after Nick Read left in December, when he said it was the right moment for a new leader.

"To realise our potential Vodafone needs to change," she said in a statement. "We know we can do better. My focus will be to improve the service for our customers, simplify our business and grow."

Della Valle's strongest backers included Vodafone's institutional investors, such as the company's biggest shareholder, Emirates Investment Authority, which has built up a 14.6% stake, a source told Reuters.

Shares in Vodafone were trading up 1.2% at 95 pence after the announcement.

(Reporting Paul Sandle in London and by Radhika Anilkumar in Bengaluru; Editing by Savio D'Souza, Sarah Young and Emelia Sithole-Matarise)