Social exclusion minister Hilary Armstrong will join prime minister Tony Blair in leaving her post on 27 June.
Armstrong, a former social worker, became the first Cabinet-level minister for social exclusion last May and last September produced a government action plan on the issue.
This included plans for primary care trusts and councils to identify the most excluded families in their areas, whose children would receive intensive services from health visitors and midwifes from birth until two years old.
It will be up to new prime minister Gordon Brown to decide whether he persists with having a Cabinet minister for social exclusion.
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