Sue Garrard, DWP director-general for marketing comms and customer strategy, will leave the department to join Unilever as senior vice-president of global comms on 1 January.
The hunt for her successor will only be conducted within Whitehall. Garrard said that she would be seeking a 'very rounded' individual, adding that she had three or four Whitehall candidates in mind whom she believes could handle the job.
Garrard added: 'I can't think of a more sexy place to be. We are absolutely a part of one of the biggest parts of the Government's strategy. It's very intellectual, very challenging and it's out there in the news all the time.'
But she said the DWP comms team had experienced 'natural shrinkage' during the previous months and this was expected to continue after next Wednesday's comprehensive spending review is revealed.
Garrard will leave a comms unit at the forefront of the ongoing discussions over cuts. Key issues at stake include controversial plans to cut child benefits for higher income families, as well as plans for a 'single benefit', amalgamating housing benefit, income support, incapacity and other benefits.
Former Whitehall comms director John Shield, now director of corporate affairs at Go-Ahead, said: 'Welfare reform is one of the most significant challenges facing the Government. Winning the debate and taking people with you once the reforms start to bite is no easy task. They will need a tough and savvy communicator.'