The 22-year-old's track 'Only Girl (In The World)' is currently on course to top the chart for a second week. A fully-reformed Take That are at number two with 'The Flood' - ahead of the premiere of their documentary this Saturday and X Factor performance on Sunday.
McFly score a new entry at number three with the second single from their upcoming album Above This Noise. If it retains its position, 'Shine A Light' - which features Taio Cruz - will become the groups 16th top five hit.
Shayne Ward's comeback single 'Gotta Be Somebody' lands at number six following his performance on The X Factor last weekend.
Elsewhere in the chart, 'Raise Your Glass', the lead single from Pink's Greatest Hits LP, is at number 12, while the Royal British Legion's '2 Minute Silence' sits just inside the top 20.
Over in the album chart, Susan Boyle is set to score her second number one album.
The Gift is the follow-up to I Dreamed A Dream, which has sold 1.8million copies in the UK. It currently has a comfortable lead over last week's number one from Cheryl Cole and Bon Jovi's Greatest Hits collection.
James Blunt's third LP Some Kind Of Trouble is currently in fourth position. The singer's previous two albums both topped the UK chart.
Elsewhere in the top ten, Cee Lo Green scores a new entry with The Lady Killer.
The final chart positions will be confirmed on Sunday on BBC Radio 1.
Source: Official Charts Company