trying to ensure houses are built - Public forum - Planning Advisory Service (PAS)

hi does anyone have any advice on where a planning permission has been conditioned to try to ensure it was 'substantially' underway within a set time (eg: two years). The reason for this would be to try to prevent developers from simply sitting on a consent (or doing the bare minimum by way of commencement) by requiring for example 50% of the total houses approved to have been started within say 2 years. This could change depending on the size of the development. ALternatively could a successful applicant be required to pay a financial penalty if a development had not reached a certain stage within a set time limit from the date of permission being granted?