General Motors Corp. has been putting enormous pressure on the Carter administration to loosen fuel economy standards set for the next five years.

GM is using its promise to comply with the wage-price guidelines as a handle for a sympathetic ear at the White House, administration sources say.

"I've never seen them put on so much pressure," one source said. "They have met with just about every White House aide that would meet with them, and they brought up the fuel economy standards at the auto industry summit meeting with President Carter."

One of the reasons for GM's growing outspokenness on fuel economy standards-which the company had earlier said it could meet-stems from the fact that Chrysler Corp., which traditionally leads the fight for easing regulations by citing its troubled financial situation, has not been heard from at all on this issue.

In a letter sent to President Carter yesterday, consumer advocate Ralph Nader complained that "the domestic automobile industry is mounting a full-scale attack on the motor vehicle fuel economy s t a n d a r d s," and the warned that "the Department of Transportation is systematically caving in to the domestic industry's demands for weaker standards."

Nader cited White House Aides Jack Watson and Alfred Kahn as two of the Administration officials who have met both with GM and Ford Motor Co. executives, and accused the White House of not making public the list of all such meetings.