Brooklyn Borough President Eric Adams is on board with the MTA’s decision to increase the size of its in-house police force by more than half, he said Friday.

Adams, a former NYPD cop, endorsed the plan to hire 500 additional MTA cops in a Dec. 19 letter to MTA chairman Pat Foye and Gov. Andrew Cuomo batting back concerns from Rep. Alexandria Ocasio-Cortez and others that the move will exacerbate “over-policing” of poor people of color.

“As quality-of-life concerns among straphangers continue to rise, this is a critical step to ensure everyone feel safe while navigating our subway system,” Adams wrote in the letter, which was posted online Friday.

He cited NYPD data — first reported by The Post — showing that while felonies and major crimes are down, misdemeanors have spiked this year.

“This uptick in misdemeanors contributes to a perception that our subway system is becoming less safe, undoubtedly causing many commuters to seek alternative modes of transportation,” Adams wrote.

“I understand there are some who have criticized this move, claiming it will contribute to the over-policing of young black and brown men … but many do not remember what the city was like when I served on the police force in the 1980s and 1990s,” he said.

Despite AOC’s high-profile opposition, the MTA board overwhelmingly approved the 500 new cop hires on Wednesday. The total cost to the $18 billion agency will be $250 million over the next four years, officials said.

Only Mayor Bill de Blasio’s three representatives voted against the plan.