New Jersey Republican Gov. Chris Christie has fired a top aide who orchestrated lane closures that jammed traffic for days in a local Democratic rival's town last September.

Christie, appearing at a news conference Thursday morning, apologized for the incident and said he has dumped Bridget Kelly as his deputy chief of staff, effective immediately, "because she lied to me."

The governor, long-rumoured to be planning a 2016 presidential run, said it was "stupid and deceitful" for Kelly not to reveal what she knew about the scandal when asked about the traffic tie-ups four weeks ago.

Traffic Mystery

Traffic moves across the George Washington Bridge, in Fort Lee, N.J., in this Sept. 2013 photo. (Mel Evans/Associated Press)

"I am heartbroken that someone I permitted to be in that circle of trust in the last four years has broken that trust," he said. Christie also said he is "embarrassed and humiliated."

The scandal is being called the biggest test of his political career, but Christie said he himself had no knowledge or involvement in the planning or execution of the lane closings.

An email message sent by Kelly last August, calling for the lane closures, was disclosed on Wednesday. It's one of several documents subpoenaed by New Jersey Democratic lawmakers investigating whether the move was made as political retaliation aimed at the mayor of Fort Lee, N.J., Mark Sokolich, for not endorsing Christie for re-election last fall.

The closed highway lanes led to traffic jams lasting from Sept. 9 to Sept. 13, between the George Washington Bridge and Fort Lee.

"Time for some traffic problems in Fort Lee," Kelly wrote on Aug. 13 in a message to David Wildstein, a top Christie appointee on the Port Authority of New York and New Jersey who resigned from the agency last month.

"Got it," replied Wildstein, a longtime Christie friend. A few weeks later, Wildstein closed two of three lanes connecting Fort Lee to the heavily travelled bridge, which runs between New Jersey and New York City.

Sokolich, a Democrat, called it "appalling" that the traffic jams appear to have been engineered.
 
Sokolich said the gridlock put people in danger by holding up emergency vehicles, and he added that those responsible should resign.

Wildstein appeared Thursday afternoon before a legislative committee investigating the scandal, but he refused to answer questions, citing his constitutional right against self-incrimination.

With files from The Associated Press