You can hold a general meeting and hope to get the 75 percent of votes required to declare his or her seat vacant. You could pass a motion of censure on the EC member which would be published in the minutes. Or you could just wait till the next AGM and vote them out (by replacing them with a preferred candidate.
Probably easier to offer them the otion of resigning or facing a motion of censure.
All of this is dependent on you having proof that they did this – a false accusation could lead to a nasty and expensive legal action.