Nick Kyrgios has escalated the war of words with Lleyton Hewitt, accusing the Australian team captain of 'throwing him under the bus' over his controversial United Cup withdrawal. 

The world No22 revealed he would not take part in the mixed-gender tournament just 24 hours before he was due to face Great Britain's Cameron Norrie in Sydney on Thursday.

Kyrgios said he wanted to be fully fit for the Australian Open next month and recover from an ankle injury he picked up in an exhibition tournament in Dubai last week.

But his decision left Australia in the lurch, with Hewitt slamming a 'lack of communication' over Kyrgios' controversial withdrawal.

The 27-year-old hit back on Friday, after his ex-girlfriend Ajla Tomljanovic withdrew from her match against Britain’s Harriet Dart just hours before it was scheduled on Friday evening

'I wonder if Stosur will throw her under the bus like our captain did for me…. "hard to prepare when you don’t know what’s going on”,' Kyrgios wrote on Twitter in response to a tweet from tennis journalist Jose Morgado announcing Tomljanovic's withdrawal.

Kyrgios' remarks were a thinly-veiled dig at Hewitt's comments on Thursday, when the Australian captain suggested the team had been left in the dark by their star player.

'I was in the same boat as all the other players yesterday, I didn’t know anymore,' Hewitt said.

'So it was pretty tough for everyone. It was more the lack of communication I think, for these guys not knowing.

'For the whole team, it was pretty tough not knowing what was going on for the last 24 hours. It’s more the communication, and if it was just worrying Nick, that’s one thing.'

Hewitt added he had to wait 'a little while' to receive a response from Kyrgios. Asked how communication could be improved, he replied: 'Just responding, that’s the normal way of doing it.'

Kyrgios' absence also forced Hewitt to reshuffle his pack, with Alex De Minaur promoted to play in place of his teammate before losing to Norrie in straight sets at the Ken Rosewall Arena in Sydney. 

De Minaur, who was expected to face Britain's Dan Evans and Spain's Pablo Curreno Busta, will also face Nadal next week. 

Significantly, both Norrie and Nadal are left-handed, while De Minaur had been preparing to face two right-handers in Evans and Curreno Busta.

Kyrgios' comments came after his agent, Daniel Horsfall, claimed Hewitt and the team were responsible for the lack of communication.

'I am a little confused as to why NKs [Nick Kyrgios] prep is treated any different to other players,' he wrote on Twitter. 

'These guys know as well as anyone, you do what you can to get there on the day, if you can’t make it you withdraw and update those who need to know, if it isn’t passed on, NK is not responsible.

'Secondly, if anyone in that team cared enough to reach out and check in on a fellow “teammate” every once and (sic) a while to see how they were feeling on any level. They’d know the situation.'

Kyrgios trained on the courts at Sydney Olympic Park on Tuesday to test out his injured ankle and he said informed Tennis Australia chief executive Craig Tiley and United Cup tournament director Stephen Farrow of his potential withdrawal before it was made official.

For their part, both Tiley and Farrow have defended Kyrgios, insisting there were no reasons to doubt his ankle issue was a genuine injury.

'We all worked together to try and get the best outcome,' Kyrgios told The Age on Thursday. 

'Not everyone is going to understand or see it from my side and that is okay. 

'What my team and I can control is how we go about our business and make sure who needs to know, knows - and we leave it at that.'