News of the Tory peer's planned departure came as the group announced half-year results that revealed revenue of £83.1m for the six months to June 30, down £5.8m year on year.
The move comes in the wake of a difficult period for the group, which last month issued a profit warning and in July faced shareholder pressure over a renumeration policy that would have allowed Chadlington to earn up to £2.2m this year.
Of his departure, Chadlington said: "It has been my intention for some while to stand down and I am delighted that I will do so just as the economies of the world are turning for the better, and that we have a management team which will make the most of this all-important investment plan which is now well under way. I am extremely proud of Huntsworth and what we have created."
The Huntsworth group includes The Red Consultancy, Citigate Dewe Rogerson, Grayling and Huntsworth Health.
The group’s half-year results revealed that digital revenues were up to 28 per cent, with 69 per cent of total group revenue generated from the UK and Europe. The US, Middle East and Asia-Pacific showed like-for-like revenue growth of 5 per cent.
Overall operating profits, meanwhile, were down year on year by £3.5m to £8.9m.
Of the results, Chadlington added: "At the 2013 year end we reported that we would continue our investment programme for a second year in order to build a multi-office business, to increase our digital revenues and to increase revenue growth in the US, the Middle East and Asia-Pacific, thereby reducing our high dependence on the UK and Europe. While the pace of these increases in the first half has been slower than we hoped, we are making some good progress, which we expect will continue in the second half and accelerate in 2015."
In April, former city minister Lord Myners was lined up to become chairman of the group, with incumbent Richard Sharp not seeking re-election and two further board members departing amid rumours of "tensions" with Lord Chadlington.
In other developments also announced today, John Farrell is set to step down as non-executive director, while AA CFO Andy Boland was appointed as non-executive director.
A further non-executive director is expected to be appointed in the autumn.