(Adds Renault CEO)
By John Irish
PARIS, Dec 3 (Reuters) - Renault will return to Formula One as a constructor next year after signing key contracts on Thursday to acquire the struggling Lotus team.
Announcing the move, a big boost for the sport after months of uncertainty, the French carmaker's chief executive Carlos Ghosn said he wanted the team to be competitive by 2019.
"Renault had two options: come back 100 percent or leave completely," he said in a statement. "After detailed analysis, I made my decision: Renault will be present in Formula One from 2016."
Renault signed a letter of intent in September to take a controlling stake in British-based Lotus, the team it previously owned but sold in late 2009 after a race fixing scandal involving the 2008 Singapore Grand Prix.
Lotus, who employ some 480 staff at their factory in Prime Minister David Cameron's constituency near Oxford, have struggled financially and were facing legal action and possible administration over unpaid taxes.
They had been due back in the London High Court next Monday.
Ghosn said work was under way to implement as quickly as possible the agreement concerning the acquisition, and key contracts had been signed on Thursday.
"Lotus appeared the best team to partner. We've known each other for 15 years and we were world champions together in 2005 and 2006," the statement said.
The team, which also won world championships with Michael Schumacher under the Benetton guise in 1994 and 1995 before becoming Renault, were renamed Lotus in 2011.
Sponsored mainly by Venezuelan state oil company PDVSA, with Venezuelan driver Pastor Maldonado confirmed for next season alongside British rookie Jolyon Palmer, Lotus finished fourth overall in 2013 but slumped to eighth in 2014 with just 10 points.
They ended the 2015 season that finished last weekend a respectable sixth, despite minimal investment and frequent financial obstacles in their way.
Bailiffs impounded their cars after the Belgian Grand Prix at Spa and they were locked out of their paddock hospitality in Japan due to unpaid bills.
"Our ambition is to win even if it will take time," Ghosn said. He told Le Figaro newspaper he expected the team to be competitive within three years.
Getting back into Formula One would give the group crucial exposure to emerging markets, notably Brazil, its second market, and Russia, where it is looking to win back market share, he said.
"In the world there are 450 million annual television spectators," he said. "That's very important and Renault will be the only generic make present in Formula One with its own team."
Renault have provided engines this season to Red Bull, with whom they won four championships in a row between 2010 and 2013, and sister team Toro Rosso.
That relationship has been stretched to breaking point this year due to Renault's failure to match the performance of dominant champions Mercedes in the new V6 turbo hybrid era.
Neither team was mentioned in the statement although Ghosn told Le Figaro talks were ongoing with Red Bull to provide it with an engine for next season. Toro Rosso are set to switch to Ferrari power. (Reporting By John Irish; editing by Ralph Boulton/Alan Baldwin)