Colin Turkington is now 40 points behind British Touring Car Championship leader Ash Sutton after taking sixth, third and eighth places at Silverstone.
While Rory Butcher won Sunday’s first two races, Turkington crossed the finish line fourth in race two.
However, a car violation by second-placed Josh Cook resulted in his disqualification as the Portadown man was promoted to third place.
Carrickfergus man Chris Smiley finished fourth in the third race won by Jake Hill.
It happened after Smiley clinched 13th and seventh places in the first two races.
BMW’s Turkington, who started the weekend third in the championship 35 points behind Sutton, drops to fourth in the standings.
Sutton leads with 285 points with Tom Ingram, who was second in Sunday’s first two races, now second at 36 points off the pace with Hill, two points ahead of quadruple champion Turkington.
Turkington finished 6.929 seconds behind Butcher in the first race as Ingram and Daniel Lloyd filled the rest of the podium.
In the second race, Butcher notched a fire-to-flag victory by taking on Cooks’ final lap challenge.
However, Cook’s BTC Racing car subsequently failed a post-race ride height check, which led to Ingram and Turkington being promoted to second and third.
Turkington was unable to enter the running race in race three as Smiley provided the main challenge in Northern Ireland taking fourth place behind Hill, Lloyd and championship leader Sutton.