Buchanan said after England's three-day capitulation by an innings and 99 runs in last week's fourth Melbourne Test that Pietersen distanced himself from the rest of the team and did not give the impression he was a team payer.
Pietersen, England's leading batsman with 420 runs in the Ashes series at an average of 60, said he was hurt by the suggestion but believes it is part of Australia's psychological warfare to keep demoralised England under pressure.
England must avoid defeat in Tuesday's fifth Ashes Test at the Sydney Cricket Ground or become the first team in 86 years to endure a 5-0 Ashes whitewash.
"He's probably just trying to target me and have a go at me. Australia love to have a go at individuals before series, during series and after series and I'm not really too interested," Pietersen told reporters here Sunday.
"It does hurt when people say that because I'm a massive team player.
"Australia obviously think the series is still alive and they want to win 5-0, so they're trying to get into my head and make me feel like a lone ranger, which I'm not."
Pietersen's role in the team has been under scrutiny because of his reported unwillingness to move up the order from his preferred batting position at No.5.
Coach Duncan Fletcher said Pietersen did ask to bat No.4 in the second innings in Melbourne because he was sick of being left with the tailenders, but was bowled by Stuart Clark for one.
Spinner Monty Panesar dismissed talk that the South African-born batsman was not a good team man.
Panesar said Pietersen goes out of his way to help him and other players in the nets.
"The way I've worked with him, he's been a great team player," Panesar said.
He said Pietersen helped him in the nets by simulating match situations.
"He purposely creates a situation where he looks to come after me or looks to be positive, the way Australians play," Panesar said.
"He gives me good practice and he gives me good advice on how I might counteract it -- maybe vary the pace, or change the angle.
"To be honest, the way I've worked with him he's been a great team player. He's always there to help me, even with the batting side of things.
"I don't know where these comments have come from, but from my experiences and the other team mates, Kevin Pietersen is always there helping us and he's been a good team man."
Pietersen said he was embarrassed to have let down England's supporters.
"I love winning and I'll do anything to win for England and for the nation," he said.
"One thing that has really got to me was all the expectations of the fans when we left England.
"Now we've got to go back feeling a bit embarrassed because we haven't done as well as people said we would."
Panesar said England still had spirit and energy, despite losing the first four Tests and the Ashes.
"The mood in the camp is still positive. Everyone is not down about the way things have gone," he said.
"One of the England strengths is they always come back from these sort of situations."