Xcel Energy has reportedly sued the city of Boulder, Colorado and its city council—marking the latest step in the company's ongoing effort to block the municipality from forming its own utility.

For several years, Minneapolis-based Xcel has been battling the so-called “municipalization” effort in Boulder, where voters passed a 2011 ballot measure allowing the city to replace Xcel with a municipal electric utility, contingent upon whether such a utility could offer similar rates and service as Xcel.

In August, Boulder’s city council took a step forward by approving an ordinance that authorized the purchase of certain Xcel assets. The City Council earlier this month reportedly voted to give the city the authority to issue bonds to finance a municipal utility, if it chooses to move forward and establish one.

It appeared last year that a similar battle might play out in Minneapolis, where the Minneapolis City Council held a public hearing regarding the possibility of adding a municipalization measure to the November ballot.

But the local debate fizzled out when Xcel and then-mayor R.T. Rybak indicated that they would work together to meet the city's energy goals.

Now, through its Public Service Company of Colorado subsidiary, Xcel has filed a lawsuit against Boulder, alleging that the city council overstepped its authority, according to media reports. The lawsuit was reportedly filed Tuesday in Boulder District Court.

Xcel contends that Boulder overstepped limitations imposed by the 2011 city charter amendment, which gave the city council authority to form a utility only if it first showed that the utility would be financially viable and its service would be reliable, according to the Boulder County Business Report.

Xcel's lawsuit reportedly claims that the Boulder City Council doesn't know the scope of the proposed utility or what customers it will serve, and the city hasn't shown that it can comply with the charter's cost and reliability requirements.

Xcel doesn't want to sell its assets and has said that it can help Boulder attain its clean-energy goals more quickly and cost-effectively than the city can with a municipal utility.