By Michael Levenson, Globe Staff

The US Senate campaign of Democratic Attorney General Martha Coakley for the first time today formally rejected an invitation to participate in a two-person televised debate with Republican state Senator Scott P. Brown because it would not include a little-known independent candidate, Joseph L. Kennedy.

“We are not going to do the debate under present circumstances,” Kevin Conroy, Coakley’s campaign manager, said yesterday.

Coakley’s decision to reject the proposed Jan. 6 debate sponsored by The Boston Globe, NECN, WGBH-TV, and WBUR-FM means she has agreed to participate in only one live, televised debate with Brown in the state’s major media market.

That debate will also include Joseph L. Kennedy and take place at the Edward M. Kennedy Institute in Boston on Jan. 11. Coakley has also agreed to a radio debate with both Kennedy and Brown on Jan. 5 and a televised debate with the two men on Jan. 8 in Western Massachusetts.

Brown has repeatedly challenged Coakley to appear in two additional debates to be televised in the Boston market without Kennedy, saying voters deserve a chance to see the major-party nominees emphasize their differences in a direct setting. Coakley, he said this week, was trying to “hide in the bunker and accept periodic debates.”

Coakley has said voters need to hear from all three candidates before the Jan. 19 special election.

“There are three candidates on the ballot,” Corey Welford, a spokesman for Coakley, said earlier this week. “And we believe it’s important that voters have the opportunity to hear from all three candidates on their positions and their records.”

Coakley has also been invited to participate in a debate sponsored by WCVB-TV, though it is not clear if she will attend. Station executives could not be reached last night.