Commons communications adviser Liz Parratt takes over his brief on an interim basis before a decision is made by the House of Commons Commission over whether to replace Stonborough.
Stonborough, who has worked as House of Commons strategic media adviser for three years, has held a brief that has included handling PR for Speaker Michael Martin.
Stonborough said he wished to ‘leave on a high’, having handled PR for the first-ever publication of MPs allowances, a story that was splashed across the front pages last month.
Stonborough said he was moving on to concentrate on corporate and private clients.
He told PRWeek: ‘We decided that I had done my stint and I said that I was going. I was only meant to be part-time, working three days a week, but it turned out to be round-the-clock.
‘It is probably the most challenging media environment in Britain and it’s been a very difficult decision for me to go; but not being on call 24/7 will be a relief,’ he added.
Early last year (PR Week, 10 January 2003) Stonborough was forced to deflect journalist enquiries in the face of attacks by Martin on government spin doctors and special advisers, whom he famously slammed as ‘sweat-rags’.
Parratt, who has held the post for three years, runs a four-strong team.