(Adds background, detail) PARIS, Jan 22 (Reuters) - Nature television star Nicolas Hulot announced on Monday he would not run for the French presidency, lifting the prospect of a candidacy that could have stripped votes from the main contenders. Hulot, 51, is a household name and had threatened last year to run for president if leading candidates did not sign up to an ecological pact to make the environment a top priority. "I have decided not to be a candidate in the presidential election," Hulot told a news conference that was broadcast live on French television. Opinion polls predicted he would have taken around 10 percent of votes, winning support from all sides but hurting Socialist candidate Segolene Royal slightly more than conservative Interior Minister Nicolas Sarkozy. An IPSOS survey earlier this month said he would have grabbed 4 percentage points from Royal against 3 from Sarkozy. Hulot came third in a recent survey listing France's most popular personalities, after soccer legend Zinedine Zidane and tennis champion-turned pop star Yannick Noah. Frontrunners Royal and Sarkozy have signed his ecological pact but have not fully endorsed all his proposals, such as imposing a carbon tax on polluters and appointing a deputy prime minister in charge of sustainable development. "I have chosen to trust the candidates' word and their commitment," Hulot said. Support for Greens party candidate Dominique Voynet is stuck around the 2 percent mark and surveys say she will not get any major boost from Hulot's decision not to run. Voynet was the most popular of several environmentalist candidates, each representing a different political camp within a fractious green movement.
