The Swansea-based Evening Post is one of 15 Local World dailies set to be transferred under Trinity Mirror’s control after the deal’s scheduled completion next Friday.
In an interview with BBC Wales, he said: “If (Trinity Mirror) try to run Swansea as a branch office from Cardiff it will not work. It’s fundamental that they maintain strong local resource in the city.
“The industry is shrinking so consolidation like this is inevitable, and centralisation and consolidation of itself is not a bad thing. It can be made to work. The absolutely crucial element is what local resource you keep on the patch.”
The South Wales cities of Swansea and Cardiff lie more than 40 miles apart and enjoy a fierce local rivalry.
Following the announcement of the £220m deal on Wednesday, the company revealed it would be looking to make up to £12m cost savings, including £3.2m on “content generation.”
In the BBC Wales interview, Spencer commented: “That means more journalists losing their jobs.”
He added: “If you want to produce a successful newspaper you need the right staff in the right place producing the right content with the right newspaper sales strategy behind it.
“These things have got to remain in place. With no local content, it’s not a local newspaper.
“Local newspapers are not lifestyle magazines and should not attempt to be so. They need local news, local campaigns.
“Local campaigning has always been a very strong part of the Evening Post. You’ve got to keep that content otherwise why should people bother to buy the paper.”
Trinity Mirror has so far not responded to requests for a comment.