The Secretary of State has powers to 'call-in', or to decide him or herself, any planning application. In practice this power is only used very infrequently. It is usually used when the application in question is of national significance, or is listed in regulations which state certain types of significant application that the Secretary of State must be notified of. The power is more likely to be used if the application is not in line with, or 'departs from', the development plan in place in the relevant area.
Most call-ins will happen for one of two reasons:
Once the Department for Communities and Local Government has then looked at the detail of an application, it can decide to call it in.
If it does, the decision to approve or reject the application is made by the Government and taken out of the local authority's hands.
If you have strong feelings about an application that the Secretary of State needs to be notified of, or which you believe is of national significance, you can take steps to ensure that it is considered as fully as possible.
It used to be the case that local planning authorities had to notify the Secretary of State of all planning applications they intended to approve that were not in line with the development plan. Since 2009 this isn't necessary, making it more important than ever for members of the public to inform the Secretary of State and request a call-in if they believe a local authority is due to approve an application that could be very damaging.