State-owned banks could still be forced to reveal levels of salaries and bonuses despite government's retreat on industry-wide disclosure, says leading investment consultancy

Pressure is mounting on the state-controlled Royal Bank of Scotland and Lloyds Banking Group to reveal the number of millionaires they employ, even though the coalition government is backtracking on imposing such rules across the entire banking industry.

Corporate governance consultancy Pirc argues that the two banks in which the taxpayer has stakes could be forced to provide more data about their pay scales if UK Financial Investments, which controls the taxpayer's shares in the bailed-out banks, demands that they do so. "They are the body responsible. UKFI should take up the running on this. They are effectively in control," said Alan MacDougall, managing director of Pirc, which advises investors managing more than £1.5tn of assets.

The calls for disclosure follow moves by the coalition to back down from implementing a key element of the review commissioned by the Labour government from City grandee Sir David Walker, which said that bankers' pay rates should be disclosed in bands of £1m, starting at £1m.

Labour had toughened the recommendation by publishing draft legislation setting the disclosure threshold at £500,000 before it lost the election. But last week the prime minister told the Commons that the government would be likely to need international co-operation before demanding such detailed disclosure, despite making a promise – the first pledge in the coalition's agreement for government – that it would crack down on "unacceptable bonuses".

The Liberal Democrats were this weekend keeping up the pressure up for industry-wide pay disclosure, having previously suggested that the starting point should be the prime minister's salary of £142,500.

"You can't do corporate governance in the dark. Walker's original proposals were pretty weak but they are the absolute minimum," said Liberal Democrat Treasury spokesman Lord Oakeshott.

Some City investors are concerned that if only RBS and Lloyds were forced into disclosure, they would be placed at a disadvantage to rivals. But the Association of British Insurers, which represents holders of about 15% of shares on the stock market, said it supported industry-wide disclosure.

"We were in favour of more transparency at the time of the Walker review and remain so," an ABI spokesman said.