Under the plans, Crown Post Office branches including locations in Beverley, Harrogate, Northallerton, Pontefract, Scarborough, Selby and York, will move into the high street retailer.
Across the country, about 700 Post Office jobs face an uncertain future, as a result of the proposals to franchise more than 70 branches.
As well as the plans to relocate 40 Post Offices into WHSmith, 33 more branches, which are already in the stores but still operated by the Post Office, will also be franchised.
Conservative MP Andrew Jones will raise particular concerns about plans to move Harrogate’s Crown Post Office in his constituency to WHSmith in the Victoria shopping centre.
Ahead of his Westminster Hall debate, he said that the move could make the Post Office less accessible, particularly as the WHSmith store is on two floors and there is “not much parking around”.
Mr Jones also stressed that Post Offices provide vital services such as banking, at a time when many high street bank branches are closing, and passport services.
This makes them “a critical part of our national infrastructure and I don’t want to see them in retreat”, he said.
Mr Jones said he understands why the Post Office may want to move from its existing “very large” site, acknowledging the building could be used more effectively.
But the Harrogate and Knaresborough MP insisted: “A strong viable Post Office is part of the fabric of our community.
“They are an anchor point on our high streets, they are one of the most trusted brands in the UK and I don’t want to see them in retreat, I want to see them expand and be secure for the future.”
A Post Office spokeswoman said: “The vast majority of our 11,500 Post Offices, large and small, are successfully operated on a franchise basis with retail partners. We believe this is the best approach to keeping Post Offices in main shopping locations and at the heart of communities where they play an important role in local economies.
“It is natural that communities may have concerns about proposed changes to their Post Offices, and we will be holding a consultation on the plans, as it’s very important to us that we get their input and feedback.
“We are pleased to say that under the proposals, the services at the new branch would remain the same, including everyday banking for the UK’s high street banks, online shopping returns and collections and foreign exchange.”