The BACC said the changes were necessary to enable it to be more effective in its work pre-vetting commercials. "It demonstrates our commitment to ensuring fitness for the future," a spokesman said.
The shake-up ends Maclean's 17 years at the top of the BACC. He is switching to external consultancy work, but will remain involved with the body while the changes are implemented.
However, the news came as a surprise to the advertising community, where Maclean's straight-talking and no-nonsense style made him a well-liked figure.
The new system will mean the appointment of a new head of the BACC. His or her remit will include driving the quality of the organisation's service and the introduction of technological change to improve workflow and meet increasing demands.
The BACC, which pre-clears about 90 per cent of all TV advertising, sees more than 32,000 commercials a year, three times the number it vetted in the early 90s.
"The BACC has reached a stage where the rise of technology has clearly made a restructure necessary," Andrew Brown, the chairman of the Committee of Advertising Practice, said.