On Wednesday, FIFA hit the Catalan giants with a transfer embargo for the next two windows due to irregularities found in their dealings at youth level.
Barca announced their intention to appeal, confirmed by Bartomeu in a press conference on Thursday, and the president said he felt the allegations have been levelled at his club in a bid to cause unrest.
"What we think is that someone on the outside is trying to do damage to Barca," he said.
"We are investigating that. Once we have proof of who it is, we will not be scared to look for these people.
"Everything is subject to an investigation. We are sure about what happened.
"Here we do things very well and there is someone who wants to damage us. It will all come out.
"We are looking over the validity of some documents and we will see who is behind all of this. We will fight for La Masia.
"We have been suffering a lot recently. Once we have proof of who is behind it, we will show everyone."
Bartomeu also revealed that, while he has not spoken to FIFA president Sepp Blatter, he had been in touch with secretary general Jerome Valcke, who may be sympathetic to Barca's cause.
"I have not talked to him (Blatter)," Bartomeu said. "But I have with Jerome Valcke, the general secretary. They are surprised because they think it (the punishment) is too far."
Despite the sanctions, Barca's supremo insisted that their plans would not change for next year, despite the sanctions.
"We're not concerned about next season," he said. "Our plans are as they are, we're not going to make any changes."
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