"I fight hard for my constituents and don't appreciate anyone attacking my work," he said.
Donoghue said he was not sure who was at the fundraiser or how much money was raised.
"I think my record proves itself," he said. "For 16 years, I have worked hard and passed many good bills that have served my constituents, especially in health care. I am certainly not beholden to any lobbyists."
Muldowney said he learned of Donoghue's fundraiser when he received an invitation in the mail for the event.
Muldowney said it would surprise him if any of Donoghue's constituents from Hagerstown attended the fundraiser.
"There's only one type (of person there) and that's someone looking to buy John Donoghue's vote," Muldowney said. "Special interest groups and lobbyists ... they participate in these things for one reason, to have influence over the elected person."
The fundraiser was held in Donoghue's honor at the Calvert House in Annapolis. The invitation said the event was hosted by Maryland House Speaker Michael E. Busch, Maryland Del. Kumar Barve, D-17, and Maryland Del. Peter A. Hammen, D-46.
The return address on the invitations was to Friends of John Donoghue, c/o Martin-Lauer Associates LLC., in Baltimore. According to its Web site, Martin-Lauer Associates is a Democratic political fundraising and consulting firm.
Colleen Martin-Lauer, who owns the company, said Tuesday it is the company's policy not to talk to the media.
While Donoghue said a list of everyone present at the fundraiser was not available, he did say Washington County Hospital officials were invited. They did not attend but sent a donation, he said.
He said he was not sure if anyone from Hagerstown was at the event.
Donoghue said the fundraiser was designed to reach people he works with on a committee that deals with health care.
"That particular fundraiser was designed for people from those different physician groups and hospitals," he said. "And (it was in Annapolis) so that everyone could be there for an early morning breakfast and then leave to go back to their jobs. There is nothing unusual about that at all."
According to the Maryland State Board of Elections, as of Sept. 1, Muldowney had about $41,000 more than Donoghue in his campaign account. Donoghue said this difference was not the reason he held the fundraiser in Annapolis.
Muldowney said he has never held a fundraiser outside of Washington County.
"I think it's an insult to the people who elect you," he said. "It shows that he's really lost touch with the people that he represents. The people who have been electing him are not in the equation."
For details about campaign financing go to http://mdelections.umbc.edu.