The sole win for Union came from John Render and Pete Ward in the pairs.
Royal Oak ‘A’ held on to second place despite losing 5-2 to Union ‘A’ for the second time this season.
Union were 2-0 down but won the next five frames to close the gap to the runners-up spot to four points with a game in hand.
The top two in division ‘B’ had free weeks but third-placed Royal Oak ‘B’ missed the chance to close the gap as they lost 4-3 to New Globe ‘A’.
George Hotel joined the Oak on 56 points as they beat Blue Ball 4-3.
The semi-final places in the KenFI Challenge Trophy have been decided.
Royal Oak ‘A’ pair Spencer Ward and Jamie Barstow are through after beating Claire Jackson (Union ‘A’) and Karl Reveley (Bright Steels ‘A’) respectively, as is Wayne Taylor, who had a champagne break in the first frame and took advantage of a mistake by Ron Taylor in the second to win 2-0.
Royal Oak ‘B’s Sarah Cook was the unluckiest player in the quarter-finals, after potting the black prematurely in the deciding frame against Derwent Arms ‘B’s Phil Arnold.
The Men’s Individuals semi-finals draw has paired Barstow with Royal Oak team-mate Dougie Pauley, to be played at the George Hotel, and Ward with Darren Craggs, of Bright Steels ‘A’, to be played at Malton Cons. Both ties will be played on March 3.