Tottenham have "grave concerns" over whether Uefa acted strongly enough after their fans reported being attacked by Barcelona stewards at a Champions League match.
The La Liga side were fined 20,000 euros (£17,546) on Friday for "insufficient organisation" during December's group game.
Video footage emerged after the 1-1 draw that appeared to show fans being struck with batons inside the ground.
The club and fans sent details to Uefa.
Other fans were filmed getting struck on the way into the Nou Camp.
"We have grave concerns that the punishment imposed will not act as enough of a deterrent to avoid a repeat," said the Champions League finalists in a statement.
"The treatment our fans was completely unacceptable, something Uefa has acknowledged, and some are still recovering as a result of this ordeal.
"No visiting supporters should have to experience what our fans went through that night again."
Uefa's fine was imposed on the day that Tottenham manager Mauricio Pochettino was given a one-match ban - suspended for 12 months - linked to the delayed start of the Champions League semi-final first leg against Ajax.
The Tottenham Hotspur Supporters' Trust said there had been "unprovoked and indiscriminate" assaults on fans and it planned to take legal advice.
"We submitted a detailed dossier of accounts from supporters who were caught up in that night's violence," it said.
"This decision by Uefa sends clear signals. It says supporters are fair game for security staff to do what they want to.
"It says that broadcast rights and kick-off times are more important than supporter safety. And it says Uefa is unfit for purpose."
Uefa and Barcelona have not commented on the statements.
Spurs, who will contest the Champions League final against Liverpool in Madrid on 1 June, were fined 10,000 euros (£8.758) for a delayed start to their home semi-final match against Ajax.