PORTLAND — Rep. Joseph E. Brennan said Monday if he were elected governor, he would “jump-start” the sluggish Maine economy by moving quickly to begin $200 million worth of state construction projects already approved by voters.

Accelerating state construction that already has been approved for bonding in referendum would not cost additional state money, Brennan said, but would prime the state’s economic pump.

Citing a State Planning Office report issued last week, Brennan said Maine’s construction industry had been especially hard hit by the slowdown of the Northeastern economy, and that almost 6,000 construction jobs had been lost in the last 17 months.

“If I am elected governor, I will make it a top priority to get these projects off the drawing board and under way,” said Brennan, a former two-term Democratic governor who is giving Republican Gov. John R. McKernan a strong re-election challenge.

“If I’m elected, I won’t wait to see what happens to the Maine economy,” Brennan told a small group of reporters at the Portland Jetport. “I will lead Maine’s economy into the future.”

Responding to Brennan, McKernan said the Department of Environmental Protection already had been instructed to put construction projects on a fast track. McKernan said a business task force he created already had recommended speeding up state construction projects.

“It has merit, but it’s not a new idea,” McKernan said of Brennan’s proposal. “We have been fast-tracking at DEP. We’ve asked all of them to speed up what they can.”

McKernan also again challenged Brennan to take a stand on the proposed $100 million widening of the southern portion of the Maine Turnpike, something that McKernan supports. Another $67 million worth of interchange improvements also have been proposed along the turnpike.

“That’s something that has a significant impact on the economy,” McKernan said.

Brennan has said he wants to study the turnpike project, which is unpopular with environmental groups, before taking a stand on it.

Brennan was beginning a four-to-five-week stay in Maine, with the House having recessed at 3 a.m. Sunday, and said he would be campaigning hard in Maine during the month of August.

“This campaign appears to be going very strongly,” he said. “I’ve never had a stronger response.”

The construction projects Brennan described already are authorized, with payment through long-term bond issues that have been approved by voters over the last several years.

Brennan said the authorized construction projects included $55 million worth of pollution controls, $50 million worth of building at campuses of the University of Maine System and Maine Technical College System, $31 million in roads and bridges, $24 million for prisons, $10 million for asbestos removal, $15 million for affordable housing, and $7 million in community mental-health centers.

Brennan conceded that most of the construction projects would require engineering studies and environmental approval in order to be sent out to bid.

But he said speeding up state construction, together with other state initiatives, could stimulate the economy through the multiplier effect of state spending.

“They will at the same time address critical state needs in education, transportation, housing and community development,” Brennan said.

Jerry Haynes, executive director of Associated General Contractors of Maine, welcomed Brennan’s proposals and said, “Anything we could get would be a help. Most of these projects are just waiting in the wings. It’s just a question of getting environmental permits.”

Haynes said any major state construction project would have a multiplier effect that would benefit the economy as a whole.

Besides speeding up state construction projects, Brennan offered two other proposals Monday — a new Maine State Housing Authority bond issue to provide affordable new-home construction and reduced-cost mortgages to eligible families and a Mainestreet Investment Fund.

The state fund, which he said might cost $10 million to $20 million, would offer state matching funds to local governments to improve downtown areas.