Women's "workplace revolution"

A new plan drawn up by UK Minister for Constitutional Affairs, Harriet Harman is grossly intrusive. There and here Labour is slipping back into control mode;

Under reforms introduced by Labour, employees have the right to ask their boss if they can work part-time but there is no obligation on them to agree. In the next stage of reforms being proposed, employers would have to prove the job cannot be done part-time to refuse the request.

What employer in their right mind would be trying to make a full-time job out of a part-time one? (Apart from one in the civil service)