In addition, it expects to raise a further £10bn from the sale of corporate and financial assets like the student loan book.
He said that there would be a further rolling efficiency review of all departments.
Mr Alexander said: “Government is the custodian of the taxpayers’ assets. When we no longer need them, we should sell them back at a fair price – not act like a compulsive hoarder.
“But too often, local and national government sits on an area of land which could be put to good use for the economy, housing or schools. So today we say this to businesses and communities. If there are any publicly-owned sites out there that you can make economic use of, then tell us. Unless ministers can be convinced the site is needed, then we will sell that land, at a fair price.”