United missed out on the Champions League last 16 after a 2-1 defeat in Basel on Wednesday but despite that disappointment their manager told a news conference on Friday they now needed to focus on trying to win Europe's second-tier competition.
"It's a good competition. [When] you see some of the teams left in it, it has got to be a strong competition," he told reporters.
"When I say it's a punishment for us to be in the Europa League what I mean by that is for 20 years what this club has only thought about is the Champions League. All we've thought of is winning that European Cup.
"So that's the punishment in the sense of it's a big disappointment of not challenging for [that trophy] this year, having been in three finals in the last four years.
"It's not a slight against the Europa League because it's a competition we want to win. We're in it and we'll try and win it," he added.
UEFA President Michel Platini had criticised Ferguson's comment that United had been penalised by dropping into the Europa League, saying it was an "amazing" competition.
"You shouldn't criticise the Europa League just because you've played in three Champions League finals," the Frenchman said at the UEFA executive committee meeting in Venice.
"The Europa League is a brilliant competition. It's amazing. I know Mr Ferguson would have preferred to be in the Champions League but so would many clubs who don't have that possibility."
