Justin Bieber has called on his Beliebers to do the unthinkable and help get a rival single to the UK Christmas Number One spot.

The Canadian pop star has just a narrow lead over the NHS Choir’s charity single with two days to go.

Bieber tweeted: “I’m hearing this UK Christmas race is close… but the @Choir–NHS single is for charity. So…

“So for 1 week it’s ok not to be #1. Let’s do the right thing & help them win. It’s Christmas. @Choir–NHS good luck.”

Bieber added: “This is what it’s all about. Merry Christmas :)”

The 21-year-old has seen huge success with his latest album, Purpose.

The Lewisham & Greenwich NHS Choir’s single A Bridge Over You almost closed the gap overnight and is now just 662 combined sales behind Bieber’s Love Yourself.

Proceeds from the NHS Choir’s single will go to charities including Carers UK and Mind.

It is the closest Christmas Number One race since 2009, when Rage Against The Machine’s single Killing In The Name was pitted against The X Factor winner Joe McElderry’s The Climb.

Barring a last-minute surge, this year’s X Factor winner Louisa Johnson is unlikely to have a look-in for the Christmas Number One.

Martin Talbot, Chief Executive of the Official Charts Company, said: “As well as climaxing on Christmas Day for just the fourth time in history, this year’s race for the festive Number One is looking like one of the closest ever.

“With just two days to go, it really is too close to call – possibly the most exciting battle since Joe McElderry took on Rage Against The Machine in 2009.”

The race will finish at midnight on Christmas Eve, with the result announced by 1pm on Christmas Day.