M&T Bank will not charge consumer and checking fees or impose late charges on consumer and mortgage loans though October, after it came under heavy criticism for customer disruptions in its account merger with People’s United Bank.

The move will apply to all customers involved in the conversion whether they had problems or not, a bank spokesman confirmed.

In a letter Monday to U.S. Sen. Richard Blumenthal, D-Conn., and four other U.S. senators from around New England, M&T Bank chief executive Rene F. Jones apologized for the interruptions and acknowledged the bank “came up short for those who experienced issues.”

“We recognize that many customers had interruptions in their ability to view and transact with their accounts digitally or online,” Jones wrote, in the letter, released Thursday.

Jones said front line branch and call center personnel also have been authorized to waive other fees as appropriate.

“For customers who were unable to access funds during the conversion, we will provide appropriate financial remuneration,” Jones wrote. “We have already begun to reimburse customers who have incurred late fees as a result of late credit card, utility or other payments.”

On Friday, Blumenthal, who is seeking reelection, joined with other U.S. senators from New England in ratcheting up the pressure on Buffalo, N.Y.-based M&T, demanding the bank compensate customers for late fees and other charges resulting from disruptions following M&T’s merging of accounts with People’s United Bank over the Labor Day holiday weekend.

In a joint statement Thursday, Blumenthal and the senators said: “M&T Bank’s commitment to compensate customers who were adversely impacted by the conversion – whether missing payments or denied access to their money — is a welcome step toward making things right.”

The senators — including Patrick Leahy, D-Vermont, Bernie Sanders, I-Vermont, Elizabeth Warren, D-Mass. and Edward Markey, D-Mass. — praised the prompt response from the bank. But the senators but said they would continue to monitor the situation “to make sure M&T follows through with their promises.”

“Consumers need swift relief and remedy now for the hardships and stress the conversion failures caused,” the statement said.

M&T also faced pressure from Connecticut Attorney General William Tong, also in a reelection bid, over the disruptions. The bank agreeing to report daily to Tong’s office about progress on resolving complaints coming into the attorney general’s office. Tong also pressed the bank to make customers “whole,” covering late fees and other charges if payments were delayed because of problems on the M&T’s end.

On Thursday, a spokeswoman for Tong, said the daily meetings continue to take place. So far, Tong has fielded about 200 complaints, the spokeswoman said.

M&T Bank acquired People’s United Bank in April for $8.3 billion. But M&T did not merge accounts of the two banks until earlier this month. In Connecticut, People’s United, one of the largest Connecticut-based banks, had hundreds of thousands of customers, plus more in southeastern New York State, Massachusetts, Vermont, Maine, and New Hampshire.

In his letter, Jones said the vast majority of former People’s United Bank customers were integrated smoothly into M&T account systems. In total, one million new customers with over 1.7 million accounts were involved. Complaints about the integration received directly from customers or by other means represented about 0.6% of the converted customer base.

“Of course, we recognize that other customers who have not formally complained might also have been impacted or have issues we need to address,” Jones wrote. “We are committed to resolving any such remaining issues promptly for all affected customers,” Jones wrote.

Jones noted that all of M&T’s systems “are up and running and our digital platforms, branches and call centers are operating at normal levels.”

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