Poulter fired off a brilliant 64 to be 13 under overall and will head into the final day with a slender one stroke advantage over Scott.
Scott's up-and-down round of 67 was not as flashy as Poulter's but it was good enough to keep him within striking distance and some five shots clear of third-placed Matthew Guyatt.
Guyatt could only manage a 75 on Saturday and is at seven under, while Kiwi Mark Brown is alone in fourth a shot further back.
The rest are too far back, although Northern Irishman Graeme McDowell picked up seven birdies when out nice and early on Saturday to fire a five under 67.
That score was easily the World Number 24's best of the week and was good enough to move him into a share of 13th place at one under overall.
Brown matched that score later in the day, but the two stars on show were Scott and Poulter.
Playing in the penultimate group of the day, Poulter and Scott matched each other for the majority of the round through two distinctly different looks and playing styles.
Poulter was dressed boldly in red and often cautious off the tee, while Scott was more conservatively clothed in a grey sweater and often outdriving the Englishman by over 50 metres on some holes.
The two contrasting styles were obvious to all following the marquee group and none more so than on the relatively short par four seventh.
Scott boomed his drive just a lob wedge away from the green and tapped in for his three after his approach shot stopped within a couple of feet from the hole, while Poulter made his birdie the hard way.
He had to rely on a putt from just off the green rolling in after his long iron failed to make the putting surface from quite some distance out.
The Englishman cheekily smiled at his playing partner once the ball hit the bottom of the cup as Poulter took a share of the lead for the first time during his round.
Scott joined Poulter and Guyatt out in front at the eighth when he made his third consecutive birdie, but from that point on there were only two players in contention.
It was a case of 'anything you can do, I can do better' for Scott and Poulter, with the pair going head-to-head on the inward nine and producing some outstanding golf.
They picked up another four birdies apiece on the way home and none more impressive than when they made a mockery of the short and tricky par three 15th by making a pair of twos with relative ease.
A hole later they both dropped a stroke - it was to be Poulter's only blemish for the day - and, when Scott could not get up-and-down from the back of the 17th and had to settle for a bogey, the defending champion was out in front on his own yet again.
The duo then birdied the last in style to complete the day's showdown and will once again go head-to-head on Sunday when the winner will be crowned.
