The head of Work and Income has resigned after less than a year in the job.
Janet Grossman was hired from British IT company Computer Sciences Corporation in July to head Work and Income, one of the Government's biggest spending agencies.
In a statement, Social Development Ministry chief executive Brendan Boyle says she needs to return to Britain for family reasons.
Mr Boyle says Ms Grossman's departure is regretted. He has appointed a ministry deputy chief executive, Debbie Power, as acting replacement.
Social workers are speculating the departure is linked to welfare reforms being pushed through by the Government.
The Government last month appointed a new board to oversee welfare reforms, headed by Paula Rebstock, former chair of the Welfare Working Group.
Association of Social Workers chief executive Lucy Sandford-Reed thinks the appointment of the Work and Income Board might be a reason for Ms Grossman's departure.
"There's potentially some link there - if a chief executive is going to be directed by a board that they're not able to influence," she said.
The Labour Party says it wants to know how the Government thought a board pushing serious welfare reforms could cooperate with existing welfare systems.
Labour's social development spokeswoman Jacinda Ardern says the Minister of Social Development Paula Bennett has revealed little despite questions in Parliament.
Ms Ardern plans to ask the questions again at a select committee next week.
Meanwhile, sources in the executive recruitment industry say the total cost of hiring a senior executive from Britain would be $100,000 - $150,000, on top of the salary.