In a letter to MTA Chairman Tom Prendergast, Velázquez urged the state agency "to solicit community input" through town hall meetings and "consider alternatives before finalizing this proposal."
Under the proposal, express service would run from Church Avenue to Seventh Avenue in Park Slope, followed by Jay St-MetroTech during morning and evening rush hour.
But the plan, which would tentatively begin in fall 2017, would significantly reduce F train service at local stations — Fort Hamilton Parkway, 15 St-Prospect Park, 4 Ave-9 St, Smith-9 St, Carroll St, and Bergen St stations — and increase travel times for commuters at those stops.
"Any improvements being considered to F train service must benefit all riders, not just those in a few select areas," Velázquez said in the letter dated July 19.
"MTA's 'F Express proposal' is not only unfair, but it can also disrupt the quality of life for riders and harm the economic health of affected communities," the letter continued.
The congresswoman also highlighted the thousands of residents in Red Hook who rely on the Smith-9th Street subway station, the nearest to the neighborhood. Bus service in Red Hook was also reduced in 2010, she said.
Opposition to F express service has been growing since the proposal was announced earlier this year.
Frustrated by the MTA's lack of response to concerns surrounding the plan, elected officials and residents launched a petition this month urging the MTA to improve F train service for all riders. The petition has more than 3,500 signatures as of Thursday afternoon.
City Councilman Brad Lander has been especially outspoken against the proposal, which he said would create "winners" and "losers" at express and local stops respectively.
"As we have said before, we will actively engage and solicit input from all communities affected by the proposed change," MTA spokesman Kevin Ortiz said in a statement.
The MTA has yet to announced a date for a public hearing.