One of two companies competing to bring natural gas to buildings owned by the city of Augusta has withdrawn its bid, frustrated with the city’s bid process.

In an open letter to the Augusta City Council, Brunswick-based Maine Natural Gas said it would withdraw its proposal to provide city property, including schools, with gas.

Instead, it will focus on expanding its system throughout the city.

Maine Natural Gas — owned by Iberdola USA, the same Spanish utility giant that owns Central Maine Power Co. — said the city of Augusta violated its own rules and gave an unfair advantage to its competitor by posting the bids on the city website.

In its letter, Maine Natural Gas called the city’s actions shameful and said they should be “of great concern to the residents and businesses in this fine city.”

The letter, signed by Maine Natural Gas Vice President Darrel Quimby, said, “Rather than pursuing our rights to protest, we will put all of our efforts into delivering natural gas to the residents and businesses in the city at competitive prices.”

Maine Natural Gas said at last Thursday’s City Council meeting that posting the bids on the city website gave Summit an unfair advantage because it was allowed to lower the prices it offered to the city after seeing Maine Natural Gas’ initially lower prices.