At the start of any project the Project Manager will have assessed the resource requirement.
The project will ultimately get underway based upon a number of assumptions, not least of which will be the availability of resource.
However, any project plan should take into account potential fluctuations in resource requirements.
Therefore, a good plan should already account for extra resource at set points in the schedule.
For this, the Project Manager should be aware of any strategies or constraints (recruitment embargo even for temporary staff) within the personnel department both current and impending.
Does the organization recruit internally or externally?
For example, via an agency or the use of consultants.
There may be a considerable difference in meeting your needs if specialist personnel are required.
The use of external resource may include off-site activity (for example, contractors) where control becomes an issue.
The use of external resource has particular advantages and disadvantages.
External resource is usually more expensive but can be more flexible, bringing them in just for specific tasks.
It is easier to remove or change external resource if their performance is unsatisfactory.
There may be particular areas of project management that you do not wish to source internally.
For example, training, health and safety skills or auditing.
See other comments below.
Whatever strategy is adopted, clear criteria are needed to filter personnel and shorten the recruitment process.
It may be prudent to liaise with the personnel department.
Filtration criteria could include:
When a member of staff leaves, whether due to temporary status or to further career prospects, the team loses valuable expertise that may be difficult to replace.
The use of external resource will almost certainly be more expensive than internal.
Replacement of this lost expertise requires a succession strategy.
Permanent resource will be being paid whether they are working or not.
Temporary staff may not have the necessary expertise and thought needs to be given to training.
Even with good training external resource may take a little time to get up to full speed.
The project team may well consist of several members that are key to the success of the project.
If or when they leave you need to have someone to replace them.
One method of achieving this is to plan to train internal resource to take over should the need arise.
If the concern is replacing a consultant this may not be so easy.
One solution might be to arrange for the consultant to train a member of the internal resource for when this person leaves.
This strategy can be used for any planned loss of key personnel
Key personnel will be on notice to leave, as part of their contracts, which will usually be at least 1 month and could be up to 6 months.
The period will reflect the length of time to recruit someone with the necessary skills or to train another.
It would be unusual to recruit permanent staff to fill a gap in resource.
However, they may have the advantage in that any trained skills can be retained and they are cheaper.
If it is not possible to obtain personnel that fully meet criteria any implications for the project should be recorded.
Other aspects that may warrant consideration are: