Speaking on CNBC’s Marketing Media Money, Clark said the positioning was "incredibly powerful" to begin with but one that ultimately was "no longer truthful".
In particular, he noted that the positioning was inaccurate after HSBC began cost-cutting and exiting smaller markets.
"[It] became something that didn't position us in the way in which was truthful about the nature of our business," he said.
"We weren’t the world's local bank. We didn't have branches in places like Thailand anymore. And so it sort of is slightly disingenuous to sort of claim to be it."
HSBC has been trying to ditch the "world’s local bank" tag since 2011, after the bank announced a round of cost-cutting. At the time, it said it couldn’t justify the description, and tasked Clark with moving away from the tagline he established when joining HSBC in 2001.
Earlier this year, HSBC announced another round of cuts, freezing salaries and hires and looking to reduce costs by $5bn (£3.86bn) by 2017, according to Reuters.
Rethinking the marketing strategy was made more challenging by the scandals that engulfed the bank. In 2012, the bank settled US probes of money launding, in 2014 it was fined for forex rigging and in the next year it was embroiled in questions over tax avoidance.
"I think banking didn't necessarily do itself as many favours as it could have done really and I think it's difficult being the sort of marketing guy in the midst of all of that stuff," said Clark. He added that the "grown-up" approach was the rally round and deal with issues as a team.
Clark announced in June that he would be stepping down from his position after 15 years at HSBC. Asked on the programme about his future plans, he said he would remain in his post until February 2017 to find a successor, after which point he will retire. However, he expressed an interest in taking a position at Chinese online giant Tencent if it expands to the UK.