(Adds complaint by losing consortium and context)
LIMA, June 30 (Reuters) - A consortium formed by Brazilian construction company Odebrecht and Spanish utility Enagas won the rights to build and operate a $4 billion natural gas pipeline in Peru, the government said on Monday.
The pipeline is key to President Ollanta Humala's delayed plans for boosting domestic natural gas output to feed a future petrochemical hub and meet fast-growing electrical demand as large mining projects come online.
The consortium will invest between $3.6 billion and $4 billion to build the 1,000-km long (620-mile) pipeline, and charge $7.329 billion for services offered during the 34-year concession, said the state agency responsible for public tenders, Proinversion.
Odebrecht has a 75 percent stake in the project and Enagas controls the rest, the Brazilian firm said.
The pipeline - the second to move natural gas from Peru's abundant Camisea fields in the jungle through the Andes and to the coast - will be built within five years, said Proinversion.
The new connection will run to the southern coastal city Moquegua instead of to the capital Lima where the existing pipeline ends.
The government announced plans to build the pipeline after Odebrecht's plans for a similar project were held up by financing.
About half of the global mineral exporter's electricity is generated from natural gas and its plans to build petrochemical plants have hinged on a new, secure supply from Camisea.
Proinversion disqualified a competing consortium, formed by the French firm GDF Suez, U.S.-based Sempra Energy and other companies, after reviewing its technical proposal.
The losing group said Proinversion broke bidding rules by not giving it enough time to respond to an inquiry about the stake each company has in the consortium, and that it would have won the concession because it offered lower operating fees.
Proinversion and the energy and mines minister denied any irregularities in the tendering process in a press conference late on Monday, saying the group changed key components of its original submission at the last minute.
The public-private concession is the second marked by controversy this year. In March, Proinversion awarded a $5.66 billion contract for a subway line to the sole bidder after two competitors unexpectedly dropped out of the contest - triggering speculation that the process might have been flawed.
Humala's government has said it would award some $13 billion in infrastructure concessions this year in a bid to spur economic growth.
(Reporting By Teresa Cespedes; editing by Andrew Hay)