State lawmakers blasted MTA officials Wednesday in a blistering letter accusing the agency of flouting public meetings laws by deliberately hiding details surrounding the MTA’s next five-year capital plan — which is due Oct. 1.

The 14 state senators, headed by Manhattan Democrat Liz Krueger, penned a letter to chairman Pat Foye, excoriating the agency for failing to hold even a single public meeting on its last capital plan — which covered 2015 to 2019.

They claim the action posed a direct violation of the state’s Open Meetings Law.

Good-government groups argue the law requires the MTA’s four-member Capital Plan Review Board to meet in public when it reviews and approves the plan, following the Oct. 1 deadline.

Yet the CPRB — whose members are selected by the legislature, governor and mayor — did not hold a single public meeting ahead of the $32 billion, five-year capital plan approved in 2014.

With a vote on the next plan just weeks away, advocates worry the MTA is trying to sweep the details of the plan, which could top $50 billion, under the rug.

“There’s going to be little to no public vetting of the plan before the vote,” said Reinvent Albany’s Rachael Fauss.

“If more details in the draft plan are out now, these kinds of negotiations and discussions could be happening publicly sooner.”

The state senators warned the MTA honchos to learn from their mistake.

“The MTA is not only a massive recipient of taxpayer dollars, it is also a vital lifeline that millions of New Yorkers rely on every day,” Krueger said in a statement.

“That is why it is so important that when critical decisions are made by the MTA, they be made in public. New Yorkers must be able to not only monitor the process of these MTA boards, but also provide input to shape the final product. I hope the MTA will follow the letter and the spirit of the law going forward.”

The lawmakers also called for the MTA to recognize that the Traffic Mobility Review Board, the authority charged with implementing the city’s congestion pricing plan, must also be held to the same standard.

“Given the impact of Central Business District Tolling, its vast number of stakeholders, and its directive to consider such subjective factors as ‘public impact, public safety, and hardships,’ we believe it is of utmost importance that the TMRB conduct a robust process of public engagement,” the legislators insisted.