Chadlington spoke to PRWeek after the announcement this morning, and amid media reports that the move had been prompted by shareholder unrest in recent months.
"I made the decision before that happened, and was not swayed by that one way or the other," said the Tory peer, who revealed he had discussed the matter with his family last year in a conversation prompted by the death of a close friend.
In June, a third of voting Huntsworth shareholders opposed the group’s proposed renumeration policy, and around 30 per cent of investors abstained from voting for Lord Chadlington’s re-election to the board.
The following month, the group issued a profit warning, driving the company's share price down by as much as 19 per cent in early trading.
However, Chadlington defended the group’s recent results, pointing to continuing investment in staff – particularly at Grayling – as one of the key reasons behind the figures.
"I was disappointed some shareholders didn’t like the investment programme but that is their right. They don’t seem to like the fact that we’re investing in people ahead of the curve, which will reduce profitability. The board of Huntsworth all wanted to do the programme [of investment], but I’m CEO so I get the brickbats."
A known confidante of Prime Minister David Cameron, Chadlington made his name with Shandwick – the predecessor to Weber Shandwick – which he founded in 1974 and built to become a global powerhouse before selling to The Interpublic Group in 1996.
He remained chairman of Shandwick until becoming CEO of Huntsworth in 2000 shortly after buying a 29.9% stake in the group, which he built to number more than 70 offices worldwide.
Chadlington, who stated that he had wanted new chairman Lord Myners in place before announcing his departure, would not give a time frame on when he will step down, adding that it would take place once a recruitment process for his successor was completed.
However, he maintained that he would remain closely involved in the business as a senior advisor "working on major new business and existing clients".
Reflecting on the current state of Huntsworth’s businesses, Chadlington told PRWeek that the group was "very well advanced" in making Huntsworth Health a "digitised offering" that put it "well ahead of the market".
However, he conceded that "we’ve not been as quick in doing that in other parts of the business", and warned that the rest of the industry still had more to do in this area.
"I worry all the time that if the industry doesn’t grasp this opportunity we will wake up and find new and emerging digital companies have eaten our lunch."
Chadlington’s business now works across more than 30 countries, with a pledged acquisition drive likely to develop a presence in Asia-Pacific already strengthened following last year’s tie-in with BlueFocus.
And despite recent poor performance, the group was tempting enough for Matthew Freud to invest in around £4m of shares last month, reportedly stating that "I recognise a decent PR business when I see one."
But, having built a globe-spanning marcoms empire, when asked about what in his career he was most proud of, the 72-year-old referred to an email that he had received this morning.
"It was from a someone saying they had been in PR for ten years and learnt a lot from the things I’d done," he said.
"It has been great to hear from others who feel I’ve influenced their lives."