More than a dozen political donors who supported Montgomery County Executive Douglas M. Duncan's "End Gridlock" slate violated state campaign finance limits and should be prosecuted, the director of Common Cause/Maryland said yesterday.

James Browning said his group identified six individuals and seven corporations, many with ties to developers, that exceeded the $10,000 limit Maryland places on donors during a four-year election cycle. Some surpassed the $4,000 ceiling on contributions to a single candidate with their gifts to Duncan, a report by the group says.

The donations helped finance Duncan's reelection bid and underwrite his successful effort to remake the County Council with members who support his transportation initiative.

"These big-dollar donors are clearly influencing the debate in Montgomery County," Browning said. "There are so many violations that we have to start dealing with this issue with legal action."

Lib Tolbert, Duncan's campaign committee chairman, said yesterday that she welcomed the Common Cause review. She promised to cooperate fully with any investigation.

"If, in fact, excess contributions have been made, the Duncan campaign will immediately take appropriate corrective action," Tolbert said in a statement.

Maryland State Prosecutor Stephen Montanarelli said yesterday that he has not seen the Common Cause report. He pledged to investigate any possible violations of the campaign finance limits that come to his attention but added that such cases are difficult to prosecute.

"We've handled a number of them, and the difficulty that arises is that we have to prove that [the excessive contributions were] willful," Montanarelli said. Moreover, he said, sophisticated donors have devised a range of legal maneuvers to circumvent the limits.

One of the companies listed as a violator in the Common Cause report is Oxbridge Development, a major Montgomery County builder owned by Sami Totah. The report says Totah's company gave $13,975 during the most recent election cycle, but Totah said yesterday that he is not in violation because the gifts were sent by different entities that operate under the same name.

"I'm aware of the limits, and I respected the limits," Totah said.

Several other donors who appear on the Common Cause list said yesterday that the government watchdog group had included them in error. The report says former Maryland senator Stewart Bainum Jr. (D) gave $12,675 to political candidates, but a spokeswoman for Bainum said $4,000 of that money came from his father, Stewart Bainum Sr.

Others said if they exceeded the limits, it was an accounting oversight. Conrad Aschenbach, owner of the King Auto Dealerships and a large Montgomery County landowner said, "If I went over, I wasn't aware of it."

Stephen Z. Kaufman, a Silver Spring land use attorney said, "I guess it's possible" that the $13,125 in donations the report attributes to him constituted a violation. He said, however, that because the checks were written on a joint account he holds with his wife, he believes the amounts fell within the legal limits for two donors.

The allegations come in the aftermath of an impressive display of political muscle by Duncan, who not only won easy reelection but also helped defeat council incumbents who opposed his pro-road and development goals.

By forming a campaign slate that allowed him to pour huge sums of his own campaign money into key council races, Duncan essentially reinvented the way campaign money is used in Montgomery County.

His effort to consolidate power had vocal detractors, and several said yesterday that the Common Cause report will be the first of several attempts to examine possible abuse of local campaign finance laws.

Anti-growth groups have been compiling comprehensive lists of Duncan's political donors and posting them on the Internet in an attempt to tie him directly to specific interest groups. And Duncan's political opponents have drafted legislation pending before the Maryland General Assembly that would allow the County Council to stiffen campaign finance laws locally.

One common thread among those cited by Common Cause was their support for the intercounty connector, a major element of Duncan's transportation plan.

Duncan's End Gridlock team used the political donations to batter former council members Blair G. Ewing (D) and Nancy H. Dacek (R) with a withering negative mail and telephone campaign that centered on their opposition to the connector. The End Gridlock team elected five candidates to the nine-member council.

Browning said that's one reason Common Cause/Maryland elected to study donations in Montgomery County. He said that the End Gridlock slate gave $26,000 to a single council candidate, Michael Knapp (D-Upcounty),which Browning said he believes helped Knapp prevail in a very close race.

"This raised questions for us about the holes that slates have blown in campaign finance laws," Browning said. The donations "had a major influence on the outcome of the election."

Montgomery County Executive Douglas M. Duncan used donations to remake the County Council with members who support his transportation initiative.