A single subway ride could soar to $3.25, a monthly bus and subway pass could hit $80, and a commuter rail pass from the farthest suburbs could climb to $338 under one proposal prepared for the MBTA to balance its budget, according to documents obtained by the Globe yesterday.

The proposals would raise the price of most trips and passes 20 to 50 percent. They emerged from analyses prepared for the T by the region’s apolitical Central Transportation Planning Staff and shared with some members of the MBTA’s official Rider Oversight Committee.

One scenario would triple the current 30-cent surcharge imposed on subway riders who use paper CharlieTickets - printed by automated fare vending machines - instead of the reloadable plastic CharlieCards. Under that plan, CharlieCard subway fares would rise from $1.70 to $2.35 and CharlieTicket fares from $2 to $3.25, a 63 percent increase.

Secretary of Transportation Richard A. Davey cautioned that the T has not released any formal proposals and would present options in January for fare increases and service cuts taking effect July 1. He said the T will hold up to 16 workshops to gather public input before the board of directors votes in the spring.

“I don’t want to release [the proposals], which could be controversial, in the middle of the holidays,’’ Davey said. “I think that’s not fair to our customers. I don’t think we’ve ever had a fare-increase or service-cuts scenario that we didn’t adjust once we put it out for public comment.’’

‘I don’t want to release [the proposals] . . . in the middle of the holidays.’

Richard A. Davey Secretary of Transportation

Davey spoke with reporters after an MBTA board meeting at which members of the T Riders Union decried the potential changes for putting the greatest burden on students, people with disabilities, and the poor.

“The MBTA is a lifeline for these riders,’’ five members of the union, a ridership group that advocates for people who depend on public transportation, wrote in a letter presented to the MBTA’s general manager and board. “They rely on the system to get them from their homes to jobs, schools, doctor’s appointments, churches, and grocery and retail stores.’’

In testimony, members said the state instead should provide more direct tax support or at least relieve the MBTA of some of its $9 billion in debt and interest. Close to half of that was inherited in 2000, when the Legislature enacted a plan known as forward funding, intended to make the T self-sufficient. Part of that was tied to expansion that was mandated to offset the environmental impacts of the Big Dig project.

Davey said such relief can come only from the Legislature and governor, unlikely given the state’s budget constraints, the sour economy, and a reluctance to raise taxes.

“In the absence of some other kind of relief, we can only work with the tools that we have,’’ Davey said. “And the tools that we have are doing everything we can to squeeze efficiencies out of our system, changing our product - which is our service - or changing the price of our product, which is the fares.’’

If the T does nothing, it faces a projected $161 million deficit for the fiscal year that starts July 1, as costs such as utilities, health insurance, and federally mandated paratransit service rise faster than MBTA revenue, the chief sources of which are fares (about $450 million a year) and a percentage of the state sales tax (worth nearly $800 million).

The T faced a similar situation last year but avoided a fare increase by implementing one-time measures such as selling future parking revenue to investors for a lump sum. The T has also tightened pension eligibility, streamlined labor costs (including switching from two operators to one operator on multiple subway lines), auctioned surplus property, and sold ads on everything from station walls to its website.

The T last raised fares Jan. 1, 2007.

The T board has not been briefed on the proposals. Members said they would like to explore a more creative fare structure, including possible zoned fares or discounts to spare students and early-morning riders from the biggest increases.

“I’m going to be a loud and proud advocate for hotel workers and hospital workers and the folks who take the early bus,’’ said board member Janice Loux, a veteran labor leader.