Bankstown pulled off a major upset as a new competition leader emerged following an enthralling round of McDonald's Women's NSW Premier cricket on Sunday.

The Sporties beat previously undefeated Sydney by seven wickets to record their first win of the season, knocking the Tigers off the top of the ladder in the process.

St George-Sutherland now holds pole position after overcoming a competitive Penrith, with Sydney, Northern District and Parramatta making up the four.

Parramatta saw off Gordon and Campbelltown-Camden defeated Universities in Sunday's other T20 games, but Bankstown's upset win was the talk of the competition.

After winning the toss and sending their hosts in at a sunny Birchgrove Oval, Bankstown struck early with the big wicket of in-form opener Naomi McDonald for just one.

Kate Barry (16) and Olivia Maxwell (29) went about re-building the innings but were separated on 34 when Barry was caught off the bowling off Jannatul Sumona (1-16)

From there the wickets just kept tumbling.

The Tigers were eventually bowled out for only 91 halfway through the 19th over.

A 48-run opening partnership between Jannatul Sumona (31) and Tahlia Dunne (21) ensured a comfortable run chase, with the Sporties bringing up victory in the 17th over for the loss of just three wickets.  

"Everything really came together for us. To beat a side like Sydney will give us a lot of confidence going forward," Bankstown coach Samantha Devlin said.

"It shows that if we back our ability we can get the job done against any side."

All-rounder Sumona, who switched from Sydney to Bankstown in the off-season, was player-of-the-match after taking a key wicket and backing it up with the game's top score (31).

Sixteen-year-old Alice Whelan was also a major contributor, picking up 2-10 from her three overs.

Parramatta made the most of Bankstown's loss, sweeping to the top of the table after chasing down Gordon's formidable 159.

An unbeaten 107-run fourth wicket-partnership between Claire Moore (55 not out) and Sophie Vaughan (44 not out) proved the difference.

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