Newspaper publisher Mark Guerringue is shutting down The Portland Sun and focusing on his recent acquisition, The Portland Phoenix, he said Friday.

The Sun’s last edition will be published Dec. 23, after which its staff will join the Phoenix to beef up and broaden the alternative weekly’s news coverage.

“Looking at the big picture, it just made a lot of sense to put all those resources from the Sun into the Phoenix,” Guerringue said.

The Sun has struggled since it was launched in 2009. Poor execution of the business plan, coupled with the recession and the resurgence of the Portland Press Herald after its purchase by financier and philanthropist S. Donald Sussman all were contributing factors to the newspaper’s troubles, Guerringue said.

“We just never got off to the start we needed to,” he said.

However, following his company’s purchase of the Phoenix in November, Guerringue said he sees the opportunity to make the Phoenix a vehicle for in-depth journalism in addition to stories about arts, entertainment and culture.

“We’re going to add some enterprise reporting with a progressive point of view,” he said.

The Phoenix’s previous editorial staff left recently to help launch DigPortland, a spinoff of alternative weekly DigBoston. DigPortland published its first issue in mid-November.

Guerringue has said the Phoenix had been somewhat neglected by its struggling former owner, the Boston-based Phoenix Media/Communications Group, and that its quality had deteriorated as a result.

The shuffling of bodies from one Portland newspaper to another has not occurred without some controversy.

Guerringue is accusing two former managers of the Phoenix, who now work for DigPortland, of violating contractual agreements and stealing business information, trade secrets and intellectual property from the Phoenix.

Jeff Lawrence, a co-owner of DigPortland, has denied adamantly that his newspaper is copying the Phoenix or has used confidential business information. Lawrence has said that anything a competitor would need to know about the Phoenix is readily available within its pages.