George Osborne, the chancellor, has urged the independent commission on banking standards to avoid "tearing up" the consensus on financial reform by pushing for a more radical separation of retail and investment banking.

Appearing before the cross-party commission, chaired by the Conservative MP Andrew Tyrie, Osborne firmly rejected the idea that the reforms proposed by Sir John Vickers to "ringfence" retail banking will fail to tackle the culture that led to the crisis.

"We have spent two years getting to this point … We are now on the verge of implementing ground-breaking legislation," he said on Wednesday. "I don't think this is the moment to tear up everything that's been done over the last two years."

Rather than questioning the Vickers reforms, the chancellor urged the committee instead to examine how bankers could adopt something akin to the ethical standards imposed on other professions.

"In the medical profession and the teaching profession, we expect certain standards, but which are administered by the profession," he said.

Barclays, whose conduct in the Libor scandal prompted Downing Street to set up the commission on banking standards, has proposed a new professional body to police the ethics of finance workers. However, Osborne faced tough questioning on how, and how quickly, he will enforce the new structure on the crisis-hit financial sector.

Lord Turnbull, a former permanent secretary to the Treasury, warned that the so-called "enabling legislation" tabled by the government to implement the ringfencing of banks' retail operations gave too little detail about how the new regime would work.

"You're not just asking us to buy a pig in a poke, you're just asking us to buy a poke – because there's not much pig in it at the moment," he said.

The chancellor said it would be up to individual banks to decide what operations, in addition to customer banking, should sit inside the ringfence, which will enforce much stricter rules on how much capital they must hold.

The committee also published an exchange of letters between its chairman, Andrew Tyrie, and the chancellor, in which Tyrie complained that the bill as tabled "does not include much detail" on how the Bank will use its new regulatory powers.

"I believe that further information at this stage would greatly assist in presentation and scrutiny of the policy, especially in respect of the definition of things which will fall either side of the ringfence," he said, in a letter sent to Osborne on 12 October.

The chancellor responded by promising to offer parliament the opportunity to examine the secondary legislation spelling out the changes in more detail in the new year.

Osborne insisted the government backed the argument of the Bank of England's executive director for financial stability, Andy Haldane, that operations inside the ringfence should be run completely separately from riskier investment banking, with distinct governance and risk management.

But he said these specific demands could not be directly enshrined in legislation, because it would be a mistake to create a "Maginot Line", reflecting how banks operate in 2012, which could later be subverted, or become irrelevant, as the operation of the financial sector changed.