The financial industry’s “white male” culture isn’t changing quickly enough, according to the U.K. regulator’s head of supervision, who said the country is unlikely to see a female chief executive officer at a major bank for at least five years.

"It’s extremely rare that in my professional life I have a conversation with a head of desk at an investment bank or a global head of business that is anything other than a white male," the Financial Conduct Authority’s Megan Butler said at the City & Financial Global’s Women in Finance Summit in London. "I’ve increasingly come to find that a little bit difficult to take."

Butler, who permanently took up the role of supervision head at the FCA in May, said a lack of diversity can lead to "group think," which was one of the problems that caused the 2008 financial crisis. While the FCA wouldn’t go as far as to introduce gender quotas, she said the regulator is exerting pressure on firms through discussions about compensation and the appointment of boards and senior executives.

When Butler started working in the City of London in the 1980s, she was almost always the only woman in the room. Now, even though she has become the supervisor for most major U.K. financial firms, not much has changed.

"For 20 years I was completely resistant to the idea of having targets on gender. I found it patronizing and insulting and I didn’t want there to be any taint on any achievement I ever had," Butler, who qualified as a barrister in 1987, said in an interview after the conference at Bloomberg in London. "But I look back and there hasn’t been significant change quickly enough."

While CEOs are often receptive to improving diversity, the most common problem identified is a lack of a pipeline of senior women to promote. One issue is the "unwritten rules" around office hours and social culture that prevent women with children from climbing the ranks.

Having faced criticism about the unequal representation of women at Davos over the years, the World Economic Forum improved a bit this year. Three of the conference’s five co-chairs were women and the percentage of female participants cracked 20 percent. But as far as having a female chief executive of a major bank goes -- we’re still some way off, she said.

"I’m going to say five years, which is an awfully long time," said Butler. "I find that quite depressing as I say that."