Roy Hodgson was under mounting pressure to justify the omission of Rio Ferdinand from his England squad after the Manchester United central defender told friends he considered the decision to be "morally very suspect" and fears increased about its capacity to unsettle the team ahead of Euro 2012.

Hodgson intensified the furore over Ferdinand's original exclusion when he called up the Liverpool full-back Martin Kelly to replace the centre-half Gary Cahill, who fractured his jaw in the friendly win against Belgium at Wembley on Saturday.

The manager has apparently not telephoned Ferdinand to explain why he has continued to overlook him and no one from the Football Association has been in contact, either, or would comment on the situation on Monday.

The official line at the outset was that Hodgson omitted Ferdinand for football reasons and it was his decision alone. The FA was unable to comment further on Monday. But Ferdinand is convinced that he has been marginalised because of the accusation of racism that his brother, Anton, made against John Terry, the Chelsea captain, who has been named by Hodgson in the squad. Terry has strongly protested his innocence and he will defend himself at Westminster magistrates court on 9 July.

Hodgson said at the time of the squad announcement that he had spoken to Terry and Ferdinand, saying: "I selected John Terry for footballing reasons and I left out Rio Ferdinand for footballing reasons. I've spoken to both of them of course. I had to do that. He [Ferdinand] was obviously disappointed. I'd be surprised had he not been. He was very gracious and he wished myself and the team the very best of luck in the tournament."

Ferdinand, 33, was furious to learn of his latest snub. Kelly has two minutes of full international experience while Phil Jones, another of the squad's defenders, is effectively Ferdinand's understudy at United. The suggestion that Kelly can also provide cover at centre‑half has not gone down well in the Ferdinand camp.

There were, though, voices in Hodgson's defence. The former England winger John Barnes said: "Everyone's international career comes to an end, it's not a question of being disrespectful in leaving someone out. I had 79 caps and I was left out because my time was over. You have to back the manager."

The Guardian's David Pleat agreed. "Nobody has a divine right to play in the side," he said. "I think it's for footballing reasons and Roy has got four players now who can cover at centre‑back. I think a right‑footer and a left‑footer in Terry and [Joleon] Lescott is a decent combination."

Ferdinand believes that Terry's upcoming trial and the issue of race is the real reason for his being sidelined and he feels badly let down not only by the FA but by Hodgson. A source close to Ferdinand told the Guardian that the player, capped 81 times, felt Hodgson's decision was "disgraceful and morally very suspect" while the source added that Ferdinand had asked "… at what point am I considered for a call-up? Is it when you get down to the Ryman League?"

The reignited issue threatens to overshadow England's preparations and it raises the prospect of the squad's black players being placed in uncomfortable situations. "Rio is very angry and he feels that every black player in Britain, every black fan and everyone in the black community has been insulted by this," the source said.

Jason Roberts, the Reading striker and anti-racism campaigner, tweeted that "Keeping up this 'Football Reasons' line where @rioferdy5 [Ferdinand] is concerned is really insulting people's intelligence now. This season has been amazing for so many reasons but it has also been a season of shame which has put us back 30 years. After what previous generations have endured, for us not to speak up on what we know is true … they must be ashamed of us."

Hodgson is not scheduled to speak publicly until Thursday in Krakow.