U.S. Sen. Richard Blumenthal Friday called on two federal agencies to investigate the disruption to consumer and business accounts in M&T Bank’s takeover of People’s United Bank, further deepening the fallout from a systems merger after Labor Day.

In a letter to the Federal Reserve and the Consumer Financial Protection Agency, Blumenthal wrote that the merging of customer accounts of the two banks over the Labor Day holiday “immediately led to chaos for far too many consumers and businesses.”

Blumenthal noted complaints about lost access to bank accounts, long wait times without resolution to problems, delays in payments and not enough customer support. He urged the agencies to take any necessary enforcement actions.

“To be clear, as a result of M&T Bank’s mismanagement of the transition, people lost access to their own money,” Blumenthal wrote.

Blumenthal’s push for federal investigations comes two days after Connecticut Attorney General William Tong accused the bank of a “serious lack of preparation” for the conversion. Tong is seeking re-election in November.

The Federal Reserve, which approved M&T’s $8.3 billion acquisition of Bridgeport-based People’s United Bank in March, said Friday it had received Blumenthal’s letter and “planned to respond.”

The consumer financial protection bureau, formed after the financial crisis in the late 2000s to investigate complaints against banks and other financial institutions, confirmed it had received Blumenthal’s request but offered no further comment Friday.

M&T declined comment Friday on Blumenthal’s letter.

But in an internal memorandum obtained by The Courant from M&T’s chief executive Rene Jones to all M&T employees, Jones noted the planning for the conversion was extensive and the vast majority of customers came onboard successfully, but “we know the experience for others fell far short of our expectations.”

Jones wrote the bank is seeing improvement in customer service areas. Call wait times in for the retail business are down 90% compared with a week ago, he wrote. Call volume fell by about 40% for the same business line over the same time period, he wrote.

Banking regulators in Connecticut do not have jurisdiction over M&T, which is based in New York.

On Friday, regulators in New York said they had received 31 complaints about the account merger, 21 from Connecticut. Those complaints were being evaluated and addressed, according to the New York State Department of Financial Services, but the department said it could not comment on any potential enforcement actions.

The department has a hotline at 800-342-3736 and can be reached by email at consumers@dfs.ny.gov. Complaints can be filed at https://www.dfs.ny.gov/complaint.

The account troubles hit particularly hard in Connecticut where People’s United Bank was one of the largest banks based in the state. M&T acquisition was completed in April. People’s United had hundreds of thousands of consumer and business customers in Connecticut.

In his letter Friday, Blumenthal, who is in the midst of a re-election campaign, wrote timely access to funds “is a critical underpinning of our financial system.”

“Any unjustified delay by a bank is unacceptable as such delay can imperil the consumers’ ability to access their own funds to pay for food or fuel or to avoid late payments on bills,” Blumenthal wrote.

Kenneth R. Gosselin can be reached at kgosselin@courant.com.