PORTLAND — West End residents who oppose a plan for offices in the parish house of the Williston-West Church say the church could be converted into condominiums and generate enough income to restore the landmark.

But a developer who has converted several West End buildings into condominiums says the site lacks adequate parking and would be too costly to convert. “The numbers don’t add up,” Jonathan Culley wrote in a letter to the Portland Planning Board.

Culley’s letter, dated Monday, is another piece of evidence in a zoning battle involving one of the city’s most important buildings and some of its most prominent residents.

After more than three hours of public testimony Tuesday night, the Planning Board postponed its decision on the plan. The board needs more time to craft a thoughtful recommendation to the City Council, said Chairwoman Carol Morrissette. The board will reconvene on the matter at 6 p.m. on May 29.

The council will make the final decision when it takes up the issue, likely in June.

Opponents of the office plan said the postponement gives them hope that the board will take their concerns into account when it drafts its recommendation.

If the board puts more conditions on the rezoning proposal, the developer, Frank Monsour, likely will reject the deal, said Orlando Delogu, a neighborhood resident and former Planning Board chairman.

Rezoning the Thomas Street parcel to allow for commercial office space could have an impact elsewhere in Portland by setting a precedent for how the city’s comprehensive plan is interpreted, said Councilor David Marshall, who represents the West End and has yet to decide how he will vote on the plan.

“It’s an incredibly complex political issue,” he said.

Built in 1877, the Williston-West sanctuary was designed by Francis Fassett, a prominent architect. In 1904, John Calvin Stevens, Portland’s most famous architect, built the parish house next door.

The Planning Board is considering whether to recommend that the current residential zone be changed to allow offices for as many as 14 workers in the church’s parish house.

Monsour, the Australian businessman who bought the church in December, plans to use the first floor of the parish house as the U.S. headquarters for his software development company, Majella Global Technologies.

He also plans to establish two or three residential units in the upper floors and preserve the sanctuary so it can be a community hall.

The rezoning agreement would require that he restore the parish house and sanctuary.

The proposal has drawn the attention of West End residents and preservationists. The Planning Board has received 91 written comments, 32 in support and 36 opposed.

At stake is the future of the church complex, which is on the National Register of Historic Places but has serious deferred-maintenance issues, said Paul Stevens, a prominent architect and a grandson of John Calvin Stevens.

“Our opponents tonight would sacrifice a very important building for the purity of (residential zoning) language,” he said.

But zoning rules that protect residential neighborhoods should not be overridden, especially for a business that does not serve the neighborhood, said Anne Pringle, a former Portland mayor who now heads the Western Promenade Neighborhood Association.

Staff Writer Tom Bell can be contacted at 791-6369 or at: [email protected]