After examining a preliminary audit of National Public Radio's finances, Rep. John Dingell (D-Mich.) said yesterday that "NPR officials and the NPR board have been guilty of financial mismanagement." Dingell warned that unless sufficient corrective remedies are taken, he will ask for public hearings.

Dingell is the chairman of the House Energy and Commerce Committee, which oversees funding of public broadcasting.

An audit, released earlier this week, of NPR financial records for the first seven months of fiscal year l983 showed a deficit of $6.5 million. It also revealed the improper use of $850,000 in employe withholding taxes, nonexistent or sloppy financial records and a generally poor internal system of controls.

"The NPR operation is effectively on the brink of bankruptcy," Dingell said. "The officials responsible for the debacle should be held accountable for their failures. Some of those officials have resigned, but others have not."

Frank Mankiewicz, NPR president, who resigned earlier, spent his last day at the Washington headquarters yesterday. Thomas Warnock, the executive vice president, also has announced his resignation.

In the last four months, since a $2.8 million deficit, later amended to $5.8 million, was announced, the management procedures and the future of the network have been of serious concern on Capitol Hill.

The news of the financial tangles broke after Dingell introduced a bill asking for an increase in public broadcasting funding. NPR would receive about $3.4 million of the $15 million that would be authorized for the Corporation for Public Broadcasting. Dingell also has asked the Government Accounting Office to conduct its own audit of the financially troubled network, which is expected to be completed in the fall.

In his statement yesterday, Dingell warned that his committee would hold hearings "if I am not satisfied with the future actions of NPR in dealing with the situation in a responsible and timely manner."

At a press conference earlier this week, Myron Jones, chairman of the NPR board, said decisions about other management-level personnel will be made at the network's board meeting Tuesday.

Even though audit officials described the company's future as perilous, Jones said, "We're wounded, but not mortally wounded."

NPR officials cited growing support by the majority of their 280 member stations to redirect $1.6 million of their funds from CPB, as well as enthusiasm from foundation and corporation officials, who had been meeting with the interim management, and unsolicited funds from listeners.