McNally, pictured, arrived at Dales Lane in June to work as number two to chairman and new manager John Allen who took the helm after the departure of former boss Richard Sneekes.
The 53-year-old, who left Hednesford in December 2015 after a second spell in charge, will continue to work for the Pics in a scouting role after a change in work circumstances left him unable to commit to the time and travelling involved in the EVO-STIK NPL's top flight.
Officials at the EVO-STIK NPL Premier Division club paid tribute to the former Northern Ireland midfielder who kicked off his managerial career as AFC Telford's first boss and has also managed Newtown, Port Talbot Town as well as coaching Shrewsbury Town.
In a statement on their website confirming the promotion of Trevor Burroughs to assistant manager, the club said: "It is a situation that Bernie feels hugely disappointed about but he will remain at the Pics in a scouting role and the club appreciates his honesty as we move towards the start of a demanding league campaign. John Allen will work with Trevor Burroughs as his assistant manager and any further managerial announcements will be made in due course."
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