Parkinson's strike in first-half injury-time was enough to secure victory
Cambridge edged out Salisbury to secure at least a play-off spot and ensure the Blue Square Premier title race will go down to the final day of the season.
Leaders Burton are three points above the U's with a better goal difference.
Cambridge must beat Altrincham next Sunday and hope Torquay beat Burton, while making up five goals on Albion.
Andy Parkinson's deflected strike after a fine run won the game for the U's after Charlie Griffin's header cancelled out Scott Rendell's strike.
Rendell had given United a 20th-minute lead from close range after good work from Chris Holroyd, but their advantage lasted just 12 minutes, with Griffin heading in Darrell Clarke's free-kick.
Parkinson's winner came in first-half injury-time after he took on several Whites defenders and cut in from the left wing before firing into the top right-hand corner, via a deflection from Neil Martin.
Burton, who led the league by 19 points at one stage, have missed chances to clinch the title in their last two games, losing to Kidderminster on Monday and Oxford on Friday.
Salisbury: Bittner, Ruddick, Martin (Sinclair 46), Pearce (Cox 65), Clohessy, Clarke, Herring, Fowler, Tubbs, Griffin, Ademeno.
Subs Not Used: Ben Osman, Toby Osman, Dutton.
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