MacLaurin's decision to quit is understood to have been driven by the constant demands of the role. He has acted as the press office for Express Newspapers - incorporating the Express titles and the Daily Star - and publications such as OK!, as well as handling personal PR for the proprietor.
It is understood that Desmond is unlikely to put the contract out to tender and is planning to appoint an in-house spokesperson.
While unlikely to replicate MacLaurin's 24/7 availability to journalists, such a move would save Desmond, renowned for his cost-cutting initiatives, a significant amount of money.
MacLaurin, who will exit the account at the end of July, is expected to continue working for Desmond on an ad hoc basis.
As one of the media industry's most controversial figures, handling Desmond's personal reputation will be a challenge. In a notorious meeting in April 2004 with Telegraph Group executives, he goose-stepped around a boardroom while making Nazi-style salutes.
MacLaurin would not comment on his decision, but claimed a shift in PR emphasis would be beneficial for Desmond. 'It would be a great result for Richard not to be seen as the only person at Express Newspapers. The focus needs to fall on editors, writers, management and products,' he told PRWeek.
It is thought that MacLaurin was often spending 50 to 60 per cent of his time on the Desmond brief, leaving little time for other clients, who include TV presenter Chris Tarrant and golfer Colin Montgomerie.
Desmond has attempted to be seen as a reputable proprietor since he bought Express Newspapers in 2000. He is reportedly readying the launch of a London evening paper and is rolling out OK! abroad.
Desmond's office declined to comment.