Democratic Rep. Tom Allen pledged this morning to denounce third-party advertisements that criticize Sen. Susan Collins, the Republican candidate in Maine’s Senate race.

"If you plan on attacking Sen. Collins, don’t," Allen said at a press conference at his campaign headquarters. "If you want to help bring change to Maine and America, stick to the issues talk about my record and my plans."

Third-party groups include the Democratic Senatorial Campaign Committee and the National Republican Senatorial Committee, as well as independent groups, such as Freedom’s Watch, a conservative group, and the liberal, web-based group MoveOn.org.

Collins’ campaign spokeswoman, Felicia Knight, called on Allen to denounce advertisements MoveOn.org ran against Collins last summer, but Allen did not.

"Last summer was last summer," Allen said, adding that he was just getting his campaign under way at that time.

Knight said in a statement that Collins "has always discouraged outside groups from running negative ads on her behalf."