AUGUSTA — The Republican-controlled Maine Senate on Monday killed a “right-to-work” bill backed by Republican Gov. Paul LePage, who said the policy is crucial if the state wants to attract investment.

The Senate voted 21-14 to follow the Democratic-controlled House in rejecting the bill, which sought to bar employers from requiring employees to join a labor union or pay dues as a condition of employment. Lawmakers also defeated two other bills that opponents called “anti-worker” measures, including one that would have prohibited public employers from deducting service fees from employees’ pay in lieu of union dues.

The bills are now dead.

A senior economic adviser for LePage told lawmakers earlier this year that right-to-work is vital if Maine wants to compete globally.

“Becoming a right-to-work state is just one piece of the puzzle Maine must embrace if we want to be competitive and attract investment and quality job opportunities,” John Butera said.

Opponents say right-to-work laws are an attempt to undermine the bargaining power of unions and drive down wages. They noted that efforts to make Maine the first New England state to adopt a right-to-work law have failed repeatedly, even when Republicans controlled both chambers of the Legislature in 2011.

“I’m thankful that common sense prevailed in the past,” said Democratic Sen. John Patrick of Rumford, former president of the United Paperworkers Union Local 900. “I don’t believe that anything has changed.”

But supporters said the bill is about freeing workers from the “shackles of compulsory unionism.”

“Right-to-work laws give workers a choice over where their money goes,” said Republican Sen. Eric Brakey of Auburn. “This freedom forces unions to earn their members’ support and it also attracts businesses and jobs.”