The Senate on Wednesday stuck with its plan to levy a tax on all short-term room rentals, such as those offered through the Airbnb online portal, an initiative the chamber’s chief budget-writer believes would raise $18 million in new revenue.

During budget deliberations, the Senate dismissed an effort by Senate Republicans to limit the proposed tax to those who rent a property for 30 days or more. Senate Minority Leader Bruce Tarr, of Gloucester, said in a statement that he did not object to taxing people engaged in the rental business, and he argued taxing everyone who rents a room even for only one night a year is the “most extreme” version of the tax.

“When we’re talking about someone who is offering their home, or a subcomponent thereof, for a shorter period of time and does it incidentally, they don’t appear to be someone who is engaged in the business of providing public accommodation,” Tarr argued. Westport Democrat Sen. Michael Rodrigues contended that as soon as someone rents their place for someone to stay short-term they are engaged in the lodging business. “You’re renting for money, for revenue. You are generating revenue. You are engaged in the business,” Rodrigues said in a statement.

Crediting Millennials for the trend, Rodrigues cited that “non-traditional lodging” is now 15 percent of the market and growing in Massachusetts. The Senate rejected Tarr’s amendment on a voice vote. In his budget, Gov. Charlie Baker proposed applying the room tax to people and businesses that provide 150 days or more of short-term rental accommodations. House Speaker Robert DeLeo has tasked Rep. Aaron Michlewit with developing a plan to tax and regulate the industry. The first hearing on the subject is scheduled for June 5 in Lenox.