* Private equity backers reduce stake to 17.1 pct
* Shares placed at 25.05 euros each -source (Adds price)
LONDON, March 19 (Reuters) - Private equity firms Cinven and Warburg Pincus have raised 1 billion euros from the sale of a 20 percent stake in Dutch cable firm Ziggo.
The buyout firms, which floated Ziggo on the Amsterdam stock exchange in March last year, sold 40 million shares in the company, Ziggo said in a statement on Tuesday without disclosing the price at which the stock was placed.
A source familiar with the matter said the shares were sold at 25.05 euros each, representing a discount of 3 percent to Ziggo's closing share price on Monday, before the sale was launched.
Shares in Ziggo, which have gained more than 30 percent since their stock market debut, closed down 5.2 percent at 24.5 euros on Wednesday.
Cinven and Warburg Pincus have been steadily reducing their holdings since last year's initial public offering, and following the latest sale they will hold a 17.1 percent stake.
Earlier this month Ziggo named Deutsche Telekom boss Rene Obermann as its chief executive from January 2014.
Ziggo, which has 2.9 million TV customers and 1.8 million broadband subscribers, was built up by Warburg Pincus which initially invested in Multikabel in 2005, and then embarked on a build-up strategy with partner Cinven.
The pair added Casema and Essent Kabelcom in 2006 and @Home in 2007, after which the company was rebranded as Ziggo. ($1 = 0.7717 euros) (Reporting by Tommy Wilkes and Kylie MacLellan; Editing by Alex Smith and Helen Massy-Beresford)