Working with project team

The Project Manager must do the ground work and needs to put down the analysis in writing as a paper to be presented to the project steering committee. It's not a naming and shaming exercise. It's the facts as clearly as they come:-

What is the skill-set that was being sought in the project ?
What was the skill-set available in house?
What was the rationale behind up-skill of the in-house staff? perhaps to keep proprietary information in-house, to increase internal capabilities, to align with organizational practices , etc
What was done to train and bring the in house staff upto speed?
What is the current situation and analysis?
What is the proposed? E.G . go to the market and find a suitable software engineer.
What is the market research? Software engineer will cost x dollars per hour and will take x amount of time to finish the project.
An analysis must also be done for the fact that if the in-house staff is able to be trained and is able to complete the work , it may take x amount of time more than an external resource.

after all the facts are presented, the Project Manager must recommend an option , which in this case will be - hiring the external resource to finish the work on time.

This may be a change request to the project and will therefore need the budget to be adjusted and additional funds required for external new software engineer or it could be increased training and more time required to finish the project.

the steering committee may direct you one way or the other according to the facts presented and the sponsor is not the only person making the decision.

The ball is in their court and whatever decision is made, the PM then abides by it.

At least you have a steering committee. It should be fairly straightforward to present the impact of the inexperienced developer on the project (ie. time), and then you can put together the justification for an expert to speed things up, at additional cost. This will come down to if either the schedule or budget constraint is more important.

Agree with Deepesh it PM to provide analysis of ground work and if he thinks some resource is not have capacity to perform as per the requirement of project and because of this project may be suffered so he acquire new resource from internal from organization or externally through CCB.