The department of health and the Social Services Inspectorate have done us all a real service by driving forward performance measurement. Social services departments are in the forefront of that within local government. Services, and to some extent outcomes, are better as a result.

But now the star-rating system has reflected unfairly on Somerset social services department. We have gone from 2 to 1 star. But how well have we done across all 49 performance assessment framework indicators?

- In 2000-1, we were "acceptable or better" on 74 per cent of all indicators and 16th best in the country.

- In 2001-2, we were "acceptable or better" on 84 per cent of all indicators and seventh best in the country.

Despite that very strong overall performance, we will suffer more audit and inspection, and have to submit more plans and have less freedoms. That will get in the way of us driving up performance from very good indeed (top 5 per cent) to the best. Everyone in Somerset wants to do that because it matters to us.

How can this happen? Last year, because government extended the scope of regulation, our inspection unit had to do 154 children's inspections instead of 22 the year before. We gave the unit extra resources, and, from doing 22 the year before, they did 143 last year. In the rush to do all that new work and transfer over to the National Care Standards Commission, they omitted 9 unannounced inspections. Not good enough, and I'm sorry that happened, but surely not enough itself to be the one factor that stopped us holding on to our two-star rating?

So, what is wrong with the star system? Mainly, the "key" performance indicators: ones where a lower performance stops the council getting above a certain rating, whatever its overall performance. Keeping the number of older people going into residential care low is one of those, but helping more adults with learning difficulties to live at home is not. Why? Re-registrations on the child protection register is a key performance indicator but the proportion of children looked after living with families is not. Does this make sense?

Government says that it wants people to know how well their social services are performing. So do elected members and staff in Somerset, and, I think, throughout the country. But, until these flaws in the star system are ironed out, it is misleading the public.

Government needs to get this right. All its good work on performance will lose credibility if it does not.

Chris Davies is director of social services, Somerset