Liverpool finished seventh last season and many believe they could struggle to get back into the top four this season if they are unable to secure new owners and extra transfer funds.
Benitez repeatedly suggested the problems last season were down to his inability to spend but, ahead of Sunday's North-West derby at Old Trafford, Ferguson has said he believes their current slump is down to the current Inter coach's poor record in the market.
"I don't know if finishing seventh last season after being second behind us the year before had anything to do with the financial position," he said. "In the last regime they spent a lot of money on players - far more than Manchester United.
"They had a huge squad of players so I don't know if that [the financial situation] is anything to do with it."
The duo had a difficult relationship during the Spaniard's six-year reign at Anfield, with Benitez famously attacking Ferguson during a press conference two seasons ago, but the United boss said: "I've never been personal. You have to examine him, not me.
"I've always enjoyed a good relationship with the Liverpool managers and both clubs have always addressed the situation properly after games. That changed under the last regime, but it's not a big issue for me."
Ferguson is on much better terms with the current Liverpool manager, Roy Hodgson.
"I have known him for a long time," Ferguson said. "I first met him in 1987 when I went on an aborted trip to Malmo. It was a European tie against Ajax and they abandoned it after one minute. He was at the game and we went for dinner afterwards.
"Roy has gathered a wealth of experience in Italy, Switzerland and Finland and the job he did at Fulham was absolutely extraordinary."
Hodgson added: "I certainly regard him as a friend. Whether he regards me as a friend you'd have to ask him. I spoke to him in a jocular way, I asked him the question 'Does it mean now I've taken the Liverpool job that we don't speak to each other?' - he didn't put the phone down but he made some cutting remark.
"The friendship hasn't been affected by me becoming Liverpool manager. I'm sure he will offer me a glass of wine when I go to the game on Sunday and I'll offer him one when he comes here, but during the match there is no room for sentiment and I'll be hoping desperately things go our way and he'll be hoping things go his way."
Despite the friendship between the two managers, United star Paul Scholes feels the rivalry remains fierce.
"You can't get away from the fact that both teams don't really like each other," he said. "We are both desperate to win and I don't think that will ever change.
"Liverpool did not have a great season last year but whenever you play them it is still a massive game. The rivalry is huge and it is good to beat them."