Proposals for S4C to take post-production in-house have been dismissed by the managing director of Wales’s largest post house, Mwnci.

Cardiff-based accountant Mike Henry’s plan was drawn up after discussions with S4C executives, and he said it could save the underpressure broadcaster up to £17m.

He said post houses can recover their initial capital expenditure on editing kit in a single production and that their charges for other productions are “nearly all profit”.

S4C does not currently undertake any post-production work in-house. But managing director of Cardiff-based Mwnci, Richard Moss, said such a move would be detrimental to the Welsh TV industry.

“The idea that people are creaming off profit because they’ve paid for the kit is rubbish - we are always looking at how we can add extra value,” he said.

Moss pointed to Mwnci’s recent £150,000 investment in Baselight grading equipment and the £200,000 it has spent upgrading to Avid Isis as examples of the level of investment made by post firms.

“When anything goes in-house, it becomes tough to keep up with technology,” he added. “If [S4C] takes it in-house, in three years time they will end up with out-of-date kit and lots of staff.”

S4C is responsible for commissioning up to 60% of the work done by the independent production sector in Wales. In October, it was announced that it was facing a 25% funding cut over the next four years.

A spokesperson for the broadcaster said it was “working on a number of possible models at this stage” and that it “welcomes all contributions to that debate”.