Luke Shaw has been taking extra training sessions at Manchester United amid his latest public row with Jose Mourinho.

While the majority of United's squad have headed off on international duty for the next two weeks, Shaw is among the few who have been left behind.

The United players not called up by their countries have been granted time off by Mourinho but while the likes of Chris Smalling have headed off on holiday after his latest England snub, Shaw has been seen at Carrington putting in extra work, according to the MEN.

Luke Shaw and Jose Mourinhohave had yet another public falling out at Manchester United

Whether Shaw hopes to regain Mourinho's favour by taking on the extra workload or simply boost his fitness is unclear.

The 22-year-old left back is reeling from his latest public dressing-down by Mourinho.

He was substituted at half-time in the 2-0 FA Cup win over Brighton last Saturday, before Mourinho then criticised his performance in a post-match interview.

A source close to Shaw told Sportsmail this week that Mourinho's behaviour is tantamount to bullying.

'I was not happy with his performance,' said Mourinho. 'I had to change one full back and I chose Luke because at least Antonio (Valencia) defensively was capable of some good positionings.'

Shaw is deeply unhappy with repeatedly being singled out by his manager. 'Mourinho's treatment of Luke is an absolute disgrace,' one source close to him told Sportsmail on Monday.

'If he has a problem with him the decent thing to do would be to keep it in-house. If this kind of abuse happened in any other workplace there would be a case for constructive dismissal. It's disgusting.'

The pair have endured a tumultuous relationship since Mourinho's arrival at United.

Mourinho blamed Shaw for one of the goals in a defeat by Watford last season and then questioned his reasons for missing another game against Swansea.

When the player responded by posting a video of himself going through a fitness workout on his day off, he was disciplined by Mourinho's No 2 Rui Faria.

Shaw played only twice in nearly four months between November and March last season, earning another rebuke from Mourinho for chatting to Bournemouth players after a bad-tempered encounter on his return to action.

United travelled to Rostov in the next game but Shaw was left behind, having been seen at Carrington hurriedly organising a photo for his visa in the belief that he was going.

He was left out of the squad to face West Brom, with Mourinho telling the media that Shaw was 'a long way behind' the likes of Young, Daley Blind and Matteo Darmian in 'the way he trains, the way he commits, the focus, the ambition'.

Shaw was removed at half-time of United's FA Cup win over Brighton on Saturday

Shaw feels he has been unfairly singled out despite doing all he can to please his manager

He sought clear-the-air talks in the manager's office and it seemed to pay off. Shaw was recalled and had re-established himself as United's first-choice left back when his season was ended by a foot injury against Swansea.

'To leave the pitch after 10 minutes, I am expecting a very big injury,' said Mourinho with a touch of sarcasm. Shaw was still on crutches when United played in the Europa League final in Stockholm nearly a month later.

He returned to action for the Under 23s in August and played for the junior side again the following month after being surprised by a late call-up and the news that he would be playing at centre back.

This season, Shaw has made only 12 starts and slipped further out of sight.

In January, he played five games back to back, the most appearances in a row since he suffered an horrific double fracture of his right leg against PSV Eindhoven in September 2015 when Louis van Gaal was United manager.

On the eve of the next match at Burnley, Mourinho spoke glowingly about Shaw. 'I can say that in this moment I don't see many left backs better than this Luke Shaw,' he said and then promptly dropped him to the bench at Turf Moor as Ashley Young returned from suspension.

Then came the dressing-down during and after the Brighton match.

While the likes of Chris Smalling have headed on holiday, Shaw is still training at United; Smalling has shared some of the highlights of his trip to sunnier climes with his wife

Chelsea are ready to offer Shaw a way out of United if he leaves Old Trafford this summer.

Shaw, who is a Chelsea fan along with the rest of his family, is likely to quit United at the end of the season - unless Mourinho goes himself.

Sportsmail understands that Shaw’s camp are aware of interest from Chelsea, who lost out to United in the battle to sign the teenager when he left Southampton for United in a £31million deal in 2014.

Manchester City, Arsenal, Everton and Tottenham - managed by Shaw’s former Saints coach Mauricio Pochettino - could also come into the reckoning if he leaves Old Trafford after four years.

It is no secret that Mourinho wants Tottenham left back Danny Rose as a replacement for Shaw.