On Monday, city officials told members of Boston’s City Council that the development deal now sitting on their legislative laps is one too good to pass up.

But Councilors also heard copious arguments, including from within their own ranks, challenging the picture Boston Mayor Marty Walsh and his administration have painted of a no-brainer win for the city – among them, an unusually sharp critique by Council President Michelle Wu, who says the city’s planning agency mislead the Council about the very project for which it now seeks special legal exemptions.

(Council President Wu and former Gov. Michael Dukakis pen Op-Ed in Boston Globe regarding Winthrop deal)

The project in question is the massive 775-foot tower being proposed by developer Millennium Partners, and which would be erected on the city-owned parcel of land known as Winthrop Square, currently occupied by a dilapidated parking lot.

And the special exemption in question – taking the form of a “home rule petition” sponsored by City Councilman Bill Linehan and supported by Mayor Marty Walsh – is waiver for the tower from laws meant to protect open spaces – Boston Common, notably, in this case – from being overshadowed (literally, that is) by tall buildings.

City officials and the project’s developers acknowledge that the building would indeed cast a shadow over Boston Common and the much-beloved Public Garden. But that shadow, city officials and developers said, would be minimal, lasting only for a few morning hours.

And the benefits would be many: about $120 million in a lump sum payment for the transfer of the land, with roughly $30 million more from subsequent development; $12 million annually in property taxes; and about $10 million in funds that would go toward affordable housing development in Chinatown.

The petition, if approved by the Council as a whole, would allow the tower to be built, shadow and all, in exchange for those benefits and with a provision that the city formally close its (already mostly-depleted) “shadow bank” – a rolling reserve of permission for otherwise-unpermitted shadows.

The petition was supported by a variety of groups; besides developers, it was supported by representatives from the Chinatown Community Development Corporation, the Boston Municipal Research Bureau, and is supported by trade union groups.  

Representatives from Friends of the Public Garden, the Boston Preservation Alliance, the Emerald Necklace Conversancy, and other advocates for the preservation of open and green spaces showed up in droves to speak against the measure.

But members of the Council Committee on Government Operations, chaired by Councilor Michael F. Flaherty, were themselves divided.

7th District Councilor Tito Jackson, who is running for mayor against Walsh, was, perhaps not surprisingly, one of the more forceful voices of criticism of the proposed exemption.

“To open an existing twenty-year law, move through one project, and close the door on other projects,” – by ending the allowance of shadow-casting developments after this one, Jackson said, “That to me, pun intended, is a shady deal.”

But at least as pointed, as perhaps more noteworthy given the political contest between Jackson and Walsh, were barbs lodged by Council President Michelle Wu.

Boston’s City Council, Wu included, had encouraged the Boston Planning and Development Agency (BPDA), formerly known as the Boston Redevelopment Authority to pursue the Millennium Partners proposal for the site (one among others by other developers).

But at the time, the BPDA hadn’t mentioned the shadow, Wu pointed out on the committee floor – a point which BPDA director Brian Golden acknowledged, saying the planning agency is working on improving its ability to review such development proposals.  

That didn’t entirely satisfy the Council president.

“Our responsibility is to conduct thorough, honest processes,” said Wu. “And if you’re saying you would have done it differently had you known – well, we know now.”

Speaking to WGBH News after leaving the hearing, Wu’s critique of the BPDA’s role in the process was more blunt.

Asked if she felt that the BPDA had “mislead” the Council by failing to divulge the issues created by the building’s shadow, Wu answered: “Yes.”

“There were multiple hearings, there was almost a year of process just in my time on the Council,” Wu said, “and not once in all of those public conversations did the shadow issue come up.”

“Folks on the [BPDA] knew about it,” Wu said, noting that BPDA director Golden said that had he himself known of the issue he would have handled the situation differently.

Nonetheless, Wu said, “We’re stuck with this false urgency around major development and revitalization of part of downtown, or nothing.”   

The rules of Boston City Council are such that the petition could be brought before the full Council by the committee’s chair, Councilor Michael F. Flaherty, as soon as the Council meets as a whole body, this Wednesday.

Wu said she was not sure how the whole Council might vote, but that Monday’s hearing showed that “from the comments today, it’s pretty clear the Council is divided on this issue.”