Monitor chief economist at Sonia Brown is leaving the organisation, HSJ understands.

Ms Brown was formerly director of European strategy at Ofgem – the energy regulator – and is moving to a role at Ofwat – the water regulator.

HSJ understands she has been a leading figure in the work to prepare Monitor to become a sector economic regulator. The organisation is taking on a significantly changed role under the government’s NHS reforms.

Monitor itself is currently deciding how to structure its governance and senior management. It has to ensure there is no conflict – or perceived conflict – between its existing responsibility for authorising and overseeing foundation trusts and its new role as sector regulator, which could see it take action directly threatening FTs’ income.

Monitor currently has a single chair and chief executive, David Bennett, and is expected to make further executive appointments once it has decided on its future structure.

HSJ last month reported senior figures in the Department of Health were calling for a greater split in Monitor’s governance than the regulator wanted itself, for example separate chairs and boards for both the two functions, and that there was a “power battle” over the issue.

However, senior sources at both DH and Monitor have since said Monitor is making the decision itself and the DH has not taken a view on the issue.

Meanwhile, Monitor’s head of media and stakeholder relations Veena Hudson is also leaving the organisation next month, to become a special adviser to deputy prime minister Nick Clegg. It is understood Ms Hudson will not be working on health in the role.