Blackwell was to be named as manager yesterday, reports the Independent, only to find he had been vetoed by Parkin, whose proposed takeover advanced over the weekend.
Blackwell wanted assurances about his future before taking the post, but was told that other candidates would be interviewed in the next few days instead.
Parkin, chief executive of the Brighouse-based Clipper Group of companies involved in haulage, warehousing and security, is an admirer of Crystal Palace boss Iain Dowie, whose side are in a First Division play-off final on Saturday.
However, he may also be keen to speak officially to Peter Jackson once Huddersfield Town are clear of their play-off commitments next Monday.
It would appear Parkin's "takeover" may yet become a "merger" in some form as it is thought one or two members of the current board are proving an obstacle and they could be asked to stay on to ensure a deal can be struck sooner rather than later.