X Factor's James Arthur set for number one hit

James Arthur's new single 'Impossible'

X Factor star James Arthur is set to top the singles chart this weekend after shifting more than 255,000 copies of "Impossible".

The Official Charts Company said the track had become the fastest-selling single of the year so far.

Debut singles by only three previous X Factor winners - Leona Lewis, Alexandra Burke and Shayne Ward - have sold more than 500,000 in their first week.

Arthur's track was released on Sunday evening, immediately after he was crowned X Factor winner.

The sales come despite Sunday's X Factor final pulling in two million fewer viewers than last year, with an average audience of 11.1 million compared with the 13.1 million who watched Little Mix win in 2011.

Changes to the show's structures are expected to be brought in next year in a bid to boost audiences.

Some judges, including Gary Barlow, could face the chop, with rumours of a return for former stalwarts Sharon Osbourne and Cheryl Cole.

PA