Former Montgomery County Executive Doug Duncan. (Katherine Frey/The Washington Post)

Former Montgomery county executive Douglas M. Duncan said Wednesday that he will continue to work as a consultant to the Lerner family, one of the Washington region’s largest real estate developers, while he campaigns to reclaim his old job next year.

Duncan lobbied for the Rockville-based Lerner Enterprises in its unsuccessful bid to land a new regional hospital and medical campus for the nearly vacant Landover Mall, which the company owns.

The former three-term county executive said he will continue to work for the Lerners on real estate projects in Greenbelt and College Park. He declined to name the ventures, and Alan Gottlieb, Lerner Enterprises’ chief operating officer, did not respond to a phone message Wednesday.

The Lerners, owners of the Washington Nationals, have extensive holdings in Montgomery, including apartments, shopping centers and office buildings. They are co-owners of White Flint Mall, which is to be demolished and rebuilt as part of a major redevelopment along Rockville Pike.

Duncan, who declined to discuss his compensation, said he sees nothing improper or inappropriate about consulting for the Lerners while pursuing his candidacy.

“I have a long history with the private sector,” said Duncan, who worked as a national accounts manager for AT&T before becoming county executive. “When you’re elected, you divorce yourself from it.” He said he will recuse himself from any Lerner-related matters if he wins election next year.

Duncan also said his work for the Lerners was confined to Prince George’s County. “I’m providing redevelopment expertise to someone, and it’s in another county,” he said.

But Duncan’s relationship with the company is likely to rekindle criticism that he is too cozy with developers and other special interests. Duncan presided over a period of enormous growth during his time in office, 1994 to 2006, including the county’s redevelopment of downtown Silver Spring in partnership with two major developers, Foulger-Pratt and the Peterson Cos.

In 2006, after inquiries from The Washington Post, Duncan returned $20,000 in campaign contributions from companies based on the Pacific islands of Saipan and Guam that were linked to disgraced lobbyist Jack Abramoff. The contributions, made in 1999, were made before Duncan authorized a lease-purchase agreement for a shuttered county school with the Yeshiva of Greater Washington, on whose board Abramoff served.

Duncan, who was running for the 2006 Democratic gubernatorial nomination in Maryland, said he was unaware of the contributions. He subsequently announced that he had received a diagnosis of depression and withdrew from the primary.

Duncan is unapologetic about his developer-friendly approach, asserting over the years that an overly cautious “paralysis by analysis” political culture had caused the county to lose economic ground to Northern Virginia and other parts of the region.

“I’m concerned that Montgomery County is getting a much bigger reputation that it is being anti-business,” he told a breakfast of Bethesda business leaders last year.

County Executive Isiah Leggett, who is running for a third term, declined to comment on Duncan’s ties to Lerner. In his 2010 campaign, Leggett received at least $5,600 in campaign contributions from Theodore N. Lerner, the founder of Lerner Enterprises, other family members and corporate officers, according to state filings.

County Council member Phil Andrews (D-Gaithersburg-Rockville), the other declared candidate in the 2014 race, said Duncan should sever his relationship with the company.

“Once someone becomes a candidate for county office, they should cease that kind of relationship,” said Andrews, who does not accept contributions from real estate interests. “The county executive, in particular, negotiates deals with developers and, for that reason, should be financially independent of them.”

Duncan did say he was ending ties with the Suburban Maryland Transportation Alliance, a business-backed advocacy group that supports increased funding for mass transportation and roads. Duncan served as chairman and also collected consulting fees.

Another notable entry on Duncan’s client list is Foulger-Pratt, which he advised in 2011 on policy matters related to Silver Spring, including Leggett’s unsuccessful proposal of a teen curfew. For months, Foulger-Pratt, developer of the troubled Silver Spring Transit Center, has been sparring with the county over who is to blame for problems that have driven the project tens of millions of dollars over budget and years behind schedule.

The Hagedorn Foundation, a Long Island-based philanthropy named for a founder of the Miracle-Gro plant food business, went to him for advice on immigration matters.

He is monitoring land-use policy decisions by the county and by the City of Rockville for the Gingery Development Group, a company with holdings along Rockville Pike. Leslie Braunstein, a spokesman for Gingery, said the firm is concerned about possible condemnation of its property as plans for a Purple Line light-rail system and a bus rapid transit network go forward.

Braunstein said that “no payments or invoices” have been exchanged but that it was anticipated the relationship would eventually involve compensation.

Duncan has also represented companies attempting to do business with Montgomery. About two years ago, he met with officials of the Public Information Office and Department of Liquor Control on behalf of Ains, a Gaithersburg software company. Nothing came of the meetings, county officials said Wednesday.

From 2010 through 2012, Duncan consulted for Milestone Communications, a Reston firm that partners with school districts and other local government entities to place cellular communications towers on their property. Milestone builds the towers, finds carriers and shares the revenue with the government agencies.

Milestone’s president and chief executive, Len Forkas, who met Duncan in the 1990s when Forkas developed the Milestone Shopping Center in Germantown, said Duncan introduced the company to county and school system officials across the state to initiate talks about partnerships. There were meetings with Montgomery agencies, such as the Montgomery County Revenue Authority, which operates the county’s golf courses, but no deals were struck, he said.

Forkas said Duncan also helped Milestone make connections with officials in Anne Arundel and Frederick counties that resulted in joint ventures. “He was a great resource for us,” Forkas said.