William B. Wrench, who last month recommended and voted for a Springfield Bypass route that would increase the value of his properties, resigned yesterday as Northern Virginia's highway commissioner under pressure from Gov. John N. Dalton.

Wrench wrote Dalton yesterday morning that he was resigning "with deepest regret." He continued to maintain that he had not acted improperly.

The resignation came one day after State Attorney General J. Marshall Coleman said Wrench clearly violated the spirit of Virginia's conflict of interest law, and after Dalton put out the word that Wrench had to go.

"I felt that his resignation would help to clear the air and allow the state highway commission to pursue the location of the bypass on its merits," Dalton said yesterday afternoon. "Accordingly, I let it be known that I thought he should resign in order to remove the appearance of impropriety that has reflected on the integrity of the commission."

Wrench, a 53-year-old Fairfax Republican who was appointed to the powerful 10-member highway commission by Dalton in 1978, is the first highway commissioner since 1967 and one of the few state officials in Virginia ever to resign because of conflict of interest allegations.

His ownership of two business parcels and one vacant lot along the bypass route he favored was disclosed in The Washington Post on Sunday. Since then, several major Virginia newspapers called for Wrench's resignation while Democrats condemned his vote and questioned Coleman's ability to investigate Wrench, who has helped raise funds for the Republican attorney general's campaign for governor.

Republicans were hoping yesterday afternoon that Wrench's resignation would end what had become an increasingly thorny campaign issue for their candidate.

"Marshall and I discussed it briefly the night before last, and he said, 'Bill Wrench is causing a few problems,' " Republican Del. Warren E. Barry of Fairfax said yesterday. On Wednesday, Coleman returned Wrench's $1,100 contribution.

"The other side has really tried to politicize this thing, and obviously it takes away from them an excuse to hold press conferences," said Coleman's campaign manager, C. Anson Franklin. "That is frankly separate from the public policy issue here, but it certainly was a concern."

Democrats continued yesterday to criticize Coleman's handling of the affair. Three Democratic state senators -- Edward M. Holland of Arlington and Adelard Brault and Clive DuVal of Fairfax -- said the Wrench case demonstrates that Coleman cannot be an effective attorney general and run for governor at the same time.

"What needs to be done now is for Mr. Coleman to resign and the General Assembly name a new attorney general so public confidence in the office can be restored," Brault said.

The Fairfax County Board of Supervisors recommended in June a 35-mile alignment for the Springfield Bypass, a $200 million road that would curve like an Outer Beltway through Fairfax. The highway commission, which has the final say on the road's route, accepted a staff recommendation last month to reject about 10 miles of the county's route with Wrench making the motion and voting for the change.

Wrench had told chief highway commissioner Harold C. King about two of his three parcels along the state route in an Aug. 14 letter, in which he also said he intended to vote. King said he saw no reason not to vote.

In a 4 1/2-page statement released yesterday, Wrench decried the "total politicization of the technical decision" over where the bypass should go.

"It is my opinion, as it was throughout my term on the commission, that my real property interests are insubstantial and my decisions while a commission member were totally unaffected by those interests," Wrench said. "To abstain from a vote on this issue would be to deny the citizens of Northern Virginia representation in this critical matter and, for that matter, in future votes which under the same criteria apparently would be in doubt.

"Therefore, I today tendered to Government (sic) Dalton my resignation . . . and requested that it be effective immediately," Wrench said.

The highway commission voted Tuesday to reconsider the route it adopted at the Aug. 20 meeting and King yesterday called a special commission meeting for next Thursday for that purpose. Fairfax supervisors and an independent consultant who studied the bypass will be invited to the meeting.

The state's route also put half of an interstate cloverleaf on a 387-acre tract owned by Milton V. Peterson and Wrench's attorney John T. (Til) Hazel Jr., an influential Fairfax lawyer-developer. Hazel and Peterson, who own several hundred acres along the county-favored route as well, both serve on Coleman's finance committee.

The Virginia Highway and Transportation Commission, one of the most powerful state agencies in Virginia, apportions highway funds throughout the state and makes many major transportation decisions. Although its members receive only $35 per meeting plus expenses, appointments to the commission are among the most coveted political plums a governor can award.

Wrench, whose four-year term would have expired next summer, represented 13 counties in Northern Virginia, including Arlington, Fairfax, Prince William and Loudoun.