And, after spurning several more good opportunities, City sealed the deal with a stunning strike from Keira Walsh midway through the second half.
The victory saw City regain top spot on goal difference in the wake of Arsenal's 4-1 home loss to Chelsea.
Having already won our first three games of the New Year, Cushing’s side couldn’t have wished for a better opening, racing into the lead after just 34 seconds.
Janine Beckie launched a raid down the right flank before switching inside to Jill Scott and the England midfielder’s accurate first time cross was met by the unmarked White who converted from close range against her former team-mates.
Beckie proved a constant threat raiding down City’s right flank in the early stages and another teasing cross on seven minutes had Birmingham defence back-pedalling once again.
City keeper Ellie Roebuck had to be alert on 23 minutes diving to her right to scramble away a dipping goal-bound 25-yard drive by Birmingham skipper Lucy Staniforth.
But with England coach Phil Neville watching on, City dominated both territory and pressure in an impressive opening 45 minutes.
On the half hour, Pauline Bremer came within an ace of doubling City’s lead. Lauren Hemp was the architect, her teasing run causing the hosts all sorts of headaches before her slide rule pass found the waiting German striker.
However, Bremer’s low show fizzed just the wrong side of the far post.
City spurned another glorious opportunity five minutes later after yet more good work by Beckie.
The Canadian spotted White unmarked at the back of the box and found her with a pinpoint cross but the England striker’s half volleyed effort was too high.
The Beckie/White axis opened Birmingham up again in the 38th, the striker’s instinctive back-heel volley from Beckie’s cross flashing just wide.
And on the stroke of half time, a succession of City corners saw the hosts under yet more intense pressure with Birmingham keeper Hannah Hampton producing a fine save to deny Gemma Bonner’s goal-bound flick.
Roebuck had to be alert to gather a Rachel Williams header as Birmingham sought to respond after the break
City thought they had a second goal when Bonner rose to meet Caroline Weir’s in-swinging corner but Birmingham defender Lucy Whipp was expertly placed on the line to keep the effort out.
Bonner then saved the day for City with a brave block to deny Rachel Williams after a quickfire break by the hosts.
However, our all-important second goal did finally arrive on 65 minutes – and it came in stylish fashion too.
Scott found space on the right channel of Birmingham defence before cutting inside for Walsh who struck a stunning first-time curling effort which went in off the left hand post.
And though Birmingham kept probing with a deflected Staniforth shot whistling a fraction wide, City ran down the clock in efficient style to seal the deal for a fifth straight win to help maintain our title charge.
How we lined up
Ellie Roebuck took her place in goal, shielded by a backline of Demi Stokes, Gemma Bonner, Steph Houghton and Janine Beckie. Caroline Weir and Keira Walsh protected the backline, employed behind Lauren Hemp and Jill Scott. The in-form Bremer and White led the line upfront.
What it means
The win saw City regain top spot on goal difference ahead of Arsenal following the Gunners' 4-1 home loss to Chelsea. City and Arsenal both have 33 points with Chelsea a point behind but having a game in hand
City are back in action next Saturday when we make the short journey to tackle Manchester United in an eagerly-anticipated Women’s FA Cup fourth round encounter.
Kick-off at Leigh Sports Village is 12.45pm as City begin the defence of the trophy we won last season.