(Reuters) - A breach of telecoms companies that the United States said was linked to China was the "worst telecom hack in our nation's history - by far", the chairman of the Senate Intelligence Committee told the Washington Post on Thursday.

Earlier this month, U.S. authorities said China-linked hackers had intercepted surveillance data intended for American law enforcement agencies after breaking into an unspecified number of telecom companies.

The hackers compromised the networks of "multiple telecommunications companies" and stole U.S. customer call records and communications from "a limited number of individuals who are primarily involved in government or political activity," according to a joint statement released by the FBI and the U.S. cyber watchdog agency CISA on Nov. 13.

Beijing has repeatedly denied claims by the U.S. government and others that it has used hackers to break into foreign computer systems.

The Chinese embassy in Washington did not immediately respond to a request for comment from Reuters on Thursday night.

There were also reports Chinese hackers targeted telephones belonging to then-presidential and vice presidential candidates Donald Trump and JD Vance, along with other senior political figures, raising widespread concern over the security of U.S. telecommunications infrastructure.

"This is an ongoing effort by China to infiltrate telecom systems around the world, to exfiltrate huge amounts of data," Mark Warner told the Washington Post.

The breach went further than the Biden administration has acknowledged, with hackers able to listen to telephone conversations and read text messages, Warner was cited as saying in a separate interview by the New York Times.

"The barn door is still wide open, or mostly open," he told the publication.