His comments came as the bank announced two new deputy governors, Monetary Policy Commitee (MPC) member Ben Broadbent and International Monetary Fund official Nemat Shafik, shaking up the top rank of the bank.
Broadbent will succeed Charlie Bean as deputy governor responsible for monetary policy in July, while Shafik will take on the newly created role of deputy governor for markets and banking from the beginning of August.
Both deputy governors will sit on the BoE's rate-setting MPC, with Shafik taking the seat currently held by the BoE's executive director for markets, Paul Fisher. The new position, will take the number of deputy governors to four.
(Read more: Carney: Strategic shake-up at Bank of England )
Shafik, who has been the IMF's deputy managing director since April 2011,will be the first female MPC member since 2010.
The BoE also announced Andy Haldane, currently the BoE's executive director for financial stability, as its chief economist from June. He will replace Spencer Dale who will take on a similar role to Haldane's current position and will leave the Monetary Policy Committee, the BoE said.
Posen, currently the president of the Peterson Institute for International Economics said the shake up of the Bank of England is only helpful if it also "embodies" a change in mindset.
"Its really not an organizational problem. To me it's a problem of they just have the wrong values," Posen told CNBC.
(Read more: Forex manipulation: How it worked )
"There was too much faith by self-regulation by the market. There was too much faith in these cosy relations. Carney can change the institutional structure, but I am hoping what is behind it is that is to embody the new mindset. If he just changes the institutions and remains this sort of laissez faire, then we got a problem," he said.
Until recently Fisher - who is executive director, markets - would have been an obvious candidate for the new position which covers much of his current job, albeit with expanded responsibilities and at one level higher in the BoE hierarchy.
(Read more: Bank of England employee suspended over forex probe )
But following the BoE's suspension of an employee this month in an internal investigation into whether staff turned a blind eye to signs of manipulation of London's $2.1 trillion-a-day currency market, the appointment of Fisher to the new role was thrown into question.
There is no evidence of wrongdoing by Fisher, who was previously the suspended employee's manager, but he came under fire last week from a parliamentary committee over his role in supervising currency markets.
Posen said in his opinion four deputy governors was too many, but he defended Fisher, instead blaming the supervision culture at the bank.
"Paul Fisher, I can say 100 percent is not corrupt in anyway, I worked with him for three years, he is a great person. But that question of the general supervisory culture at the bank, that we let those fixes go on, that we don't do things in open markets - that we have all these side conversations - that is what has to change, have a different mindset," he said.
Fisher's term on the Monetary Policy Committee - where he was one of the stronger supporters of more stimulus for Britain's economy after the financial crisis - ends in May.
Fisher has said he first heard of the currency accusations only last October, and that the alleged collusion by market-makers under investigation now was different from less serious discussions about hedge funds' activity as far back as 2006.
(Read more: Bank of England holds rates as pressure mounts )
Carney said the creation of the new role was not a response to the inquiry, but whoever fills it will conduct "a root and branch review of how we conduct market intelligence".
Former Monetary Policy Committee member Andrew Sentance said he feared the new deputy governor might be given no real authority. "In my experience, all important decisions in the Bank are taken by and announced by the governor," he said.
-By CNBC's Jenny Cosgrave: Follow her on Twitter @jenny_cosgrave
Reuters contributed to this report