The Home Office does not hold a central record of the number of applications for employment that have not passed beyond vetting procedures and it would be of disproportionate cost to assemble such a record.
The Metropolitan Police is responsible for its own vetting, I understand that the Metropolitan Police do not hold a central record and that it would be of disproportionate cost to assemble such a record.
In relation to the Security Service (MI5) and the Secret Intelligence Service (MI6), the policy of successive Governments is not to answer questions of detail about them.