• FSA revealed 2,800 bank staff got more than £1m last year • More than 2,000 City firms are covered by FSA code on pay

The UK's four high-street banks are expected to admit this year that they are employing up to 200 people each earning more than £1m as a result of the City regulator's new code on pay.

Pay experts believe that the major banks – Lloyds Banking Group, HSBC, Barclays and Royal Bank of Scotland – will reveal the figures under the Financial Services Authority's new disclosure rules on pay, which came into force on 1 January. The bank and financial institutions covered by the code – more than 2,000 firms in total – have until the end of the year to publish their bonus rules.

The FSA code, while not going as far as many critics of City pay levels would hope, will shed more light on practices in the City than ever before. The 2008 banking crisis raised questions about the way bankers were paid and the FSA introduced its first code for 2009. This was updated on 1 January when the FSA amended the code to incorporate changes demanded by the Committee of European Banking Supervisors.

Last year, the FSA revealed that the first version of its code had found that 2,800 members of staff at City firms had been paid more than £1m but did not provide a more detailed breakdown. Pay experts believe that individual banks will now have to disclose that information as banks have to provide details of the amounts paid to so-called "code staff" – those regarded as taking risks for the firm.

Jon Terry, remuneration partner at PricewaterhouseCoopers, said: "Banks will have to disclose all their code staff and by divisions. There will be some very large numbers."

He estimated that the high street banks employ between 100 and 200 such staff who in aggregate will be paid £100m.

While banks will not need to use £1m as a threshold for disclosure, they are required to provide an aggregate amount paid through each separate division allowing crude calculations to be made.

The regulator stated in an updated code in December that: "Institutions should provide aggregate quantitative information by business area and on remuneration for members of staff whose actions have a material impact on the risk profile of the institution. The information for each of the major business areas at an institution – ie investment banking business area, retail banking business area etc – should include: number of staff, total remuneration and total variable remuneration.

"More detailed qualitative information on remuneration should be disclosed for senior managers and other members of staff whose actions have a material impact on the risk profile of the institution including aggregate information on amounts of remuneration, amounts and forms of variable remuneration, and amounts of outstanding deferred remuneration."

Banks will need to decide in the next few weeks whether to make the announcement in their annual reports – where directors' remuneration is disclosed – or in separate reports later in the year.

Even so, the regulator's code is not as rigorous as critics of City pay had hoped as the government has backed down from demanding that banks detail the number of people earning more than £1m a year in £1m bands, as proposed by the City grandee Sir David Walker.

The previous Labour government had drafted legislation that would have gone further by demanding pay be disclosed in bands beginning at £500,000 to £1m, thereafter in leaps of £1m bands. George Osborne, the chancellor, refuses to support this, insisting that he needs Europe-wide support for such a measure.