Adam Cunnington scored twice as Tamworth inflicted a first home defeat of the season on Forest Green Rovers.
James Norwood had two chances for the hosts but Cunnington pounced on Tommy Wright's looping header for his 10th of the season to put Tamworth ahead.
The striker then scored from the spot after being fouled by Jamie Collins to become the league's leading goalscorer.
Collins netted a header following Magno Vieira's pass from Yan Klukowski's free kick, but Tamworth hung on for the win.
The home side twice went close to levelling a minute after closing the gap as Matt Taylor's shot was saved and Collins fired the rebound over the bar.
Substitute Vieira also had a chance with time running out but Tamworth held firm for their fifth away win of the season.
Second-placed Rovers went into the game two points behind Newport, but now find themselves five points adrift as the
Tamworth, who inflicted a second straight defeat on Forest Green, remain seventh but close the gap on the play-off places to three points.
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Forest Green Rovers manager Dave Hockaday told BBC Gloucestershire:
"We had two great chances to go ahead and we didn't take them. We were sloppy in the first half.
"I thought the lads were brilliant in the second half and we took the game to them.
"I've got to look at the positives and we deserved at least a draw.
"We're in a turbulent spell at the moment after two defeats but we've got to bounce back."