The D.C. Public Service Commission, in a rare emergency hearing, yesterday delayed consideration of a $17.8 million rate increase by Washington Gas Light Co. because the company failed to produce documents within a schedule it had agreed to.

Although Washington Gas spokesman Paul Young called the company's handling of the case a "misunderstanding," the comission's ruling comes at a time when the company continues to complain about "regulatory lag."

Washington Gas has frequently called delays in case handling by the regulatory commission a major reason for declining profits.

At issue in the commission's ruling is a series of findings required for consideration of a $17.8 million rate increase, requested in June.

D.C. People's Counsel Brian Lederer had asked Washington Gas be forced to submit information based on its 1979 data, for use as the test year in evaluating the rate hike request.

The commission had ordered Washington Gas to produce the information by Nov. 15. The gas company had not supplied cost of service, and rate of return data, for example, by that date.

"You can't conduct a hearing without testimony," Lederer said yesterday. "This ruling restarts the clock on the entire case."

Lederer suggested that Washington Gas in having a better year in 1979 than 1978 and that the company might be forced to ask the commission for a smaller rate increase.

"In retrospect, it appears that the commission is asking for a new case," Young, the gas company spokesman, said. "We didn't understand that at the time.

But Lederer maintains that the gas company's failure to produce the documentation is "no misunderstanding," and that the company is not eager to report its 1979 information.

"The company has been yelling and screaming about delay," he said. "Now they're doing it themselves."