From October 2009, if you want to work with children or vulnerable adults, you need to be registered with the Independent Safeguarding Authority. This applies to 'Regulated Activities' which includes Fostering and Childcare.
However in domestic circumstances (such as a nanny working in a child's own home) there is not a legal requirement for the employer (parents) to check the status of their employee, according to ISA Factsheet No 3. However it appears that the system being designed will enable employers to carry out this check - which is an improvement on the current CRB system.
ISA registration will initially cost £64 (see fees) and the registration IS TRANSFERABLE between jobs. The fee includes an Enhanced CRB Disclosure.
It is unclear to me how this will affect providers who are currently registered with Ofsted, though I anticipate that Ofsted will require that all providers register with ISA, who are then responsible for continual monitoring of someone's suitability to work with children.
I have only just found out about ISA while doing some research for a Musician who had posted on another mumsnet thread. So the above info is what I have found out so far. I expect it will change over the next year, but thought you would want to be made aware that this scheme does now have a go-live date, so will be something we all need to look at over the next year and have registered on by October 2009.