By North-west correspondent Alex Stevens

Leaked transfer documents show Anthony Martial could become Manchester United’s record signing if certain benchmarks are reached.

The website Football Leaks has published what appears to be an authentic transfer agreement between United and Monaco of the striker’s move last summer.

It was widely reported when Martial moved to Old Trafford for an initial £36million, which made him the most expensive teenager in the history of football, that the deal could climb beyond the £50million mark through various add-ons.

This is now confirmed by the document which, due to currency changes, means United could end up paying £61.6million for him.

This would mean Martial would replace Angel Di Maria, who cost £59.7 million from Real Madrid in 2014, as United’s biggest ever buy.

For that to happen, the France international would have to score 25 competitive goals for United, make 25 appearances for his country while at the club as well be nominated for the Ballon d’Or.

When United signed Martial in September, his proposed cost if add-ons were triggered was £58.8 million, but that has swelled to over £61.6million as the pound, which was worth 1.36 euros, is now worth 1.29 euros.

United have already paid Monaco £15.4million, which is guaranteed to go up to £38.5million with another £23.1million due to be paid by 1 July, 2016.

United will end up paying a further £7.7million if Martial scores 25 competitive goals for the club,  another £7.7million if he earns 25 France caps while at United and a further £7.7million if he is shortlisted for the Ballon d’Or.

The transfer agreement is signed by United executive vice-chairman Ed Woodward and Monaco vice-president Vadim Vasilyev.