The complaint to the ASA, laid before the expenses review was made public last month, said the Naked Bus ad portrayed Mr Brown "in a manner that could cause him to be the object of ridicule and/or hostility".
But the ASA's complaints board concluded the ad was a "humorous and satirical portrayal of Len Brown within the context of Naked Bus's brand and mobile website launch".
It found the ad did not reach the threshold of ridicule, hostility and offence.
The ASA also found there were no grounds to proceed with a complaint against a Christmas campaign for strip club Calendar Girls.
The radio ad said it was time to "jingle your bells" and continued: "Xmas at Calendar Girls will be merry and she'll be unwrapping her gifts all night."
The complainant said they were offended by the ad, and Christmas should be "about purging sin, not making more".
The ASA noted Calendar Girls promoted a legal form of adult entertainment, and was entitled to promote its business at any time of year, including Christmas.