Brocklehurst said she was taking the new title of head of PA, campaigns and communications on a seven-month interim basis.
She reports to chief executive Deborah Annetts. Her brief will include interviewing the charity's stakeholders and developing strategies for Dignity in Dying campaigns.
Brocklehurst said she was also assessing how best to use the comms resources of the charity, known as the Voluntary Euthanasia Society until January.
She left her director of comms role at Addaction at the beginning of the month after six years with the charity, and has held senior comms roles in local and central government. She was a Labour Party press officer reporting to Peter Mandelson in the late 1980s and has also been a DfES speechwriter.
Slattery said he was working out a two-month notice period before deciding on his next career step.
‘There is a certain amount of time that you can do a stressful job like this and I felt it was time to look around for something new,' he said. ‘I'm sad to be leaving [after two-and-a-half years] and I've particularly enjoyed the campaigning side of the job.'
In May the House of Lords blocked Lord Joffe's Assisted Dying Bill, prompting Dignity to vow that it would fight to have the bill introduced.
Dignity campaigns manager Keith Reed joined the General Medical Council as head of PA in the summer.
Brocklehurst's ex-role at Addaction has been filled on an interim basis by Jill Rawlins (PRWeek, 6 October).