The City Council on Wednesday unanimously passed a bill to expand the membership of the board of library trustees by four members and hand them fundraising powers.

The bill, known as a home rule petition, still needs the sign-off of the mayor, the state Legislature and the governor, was sponsored by City Councillors Michael Ross, Ayanna Pressley, and Felix Arroyo.

But it also has the support the head of the nine-member board, attorney Jeffrey Rudman.

In a Monday letter to Ross, Rudman said he could not speak for the board, but the bill had his support.

City councillors, including Arroyo, said they were shocked to learn at a hearing on the Boston Public Library's budget that the trustees did not fundraise.

But Councillors John Connolly and Bill Linehan said that while they supported the measure, they had also reservations about rushing the proposal through the council without a hearing. Connolly added that the fundraising ability might lead to conflicts of interests arising.

According to Ross, the state Ethics Commission has okayed the proposal.

Four libraries, while granted a nine-month reprieve, remain on the chopping block, including the Lower Mills branch.

The proposal to expand the board must pass the Legislature by the end of July, when lawmakers adjourn for the summer and turn their complete focus to re-election. Bills that do not make it to the governor's desk must be re-filed in January.

Mayor Thomas Menino's office did not immediately respond to a request for comment on the proposal, though councillors say they expect it to be signed.

SEE RELATED: City Council approves budget on 11-2 vote.