A shareholder rebellion is brewing before Royal Bank of Scotland’s annual general meeting as investor groups raise red flags over a pay policy that involves the chief executive receiving £350,000 per year in pension payments.

The Investment Association (IA) and individual shareholder society ShareSoc have released reports raising concern over pension payments for the bank’s CEO, Ross McEwan, which are out of line with the rest of its workforce.

McEwan is receiving annual pension payments worth 35% of his £1m salary, compared with the rest of its staff, who are offered 10%. The bank has addressed payments for its newest executive, finance chief Katie Murray, who receives a 10% pension payment worth £75,000 but has resisted making changes for its top boss.

The IA, which manages £7.7tn in assets of 250 members, has released its Institutional Voter Information Service (IVIS) report on RBS, which bears an “amber top” or warning over the bank’s remuneration report. RBS’s pay plans breach the association’s guidelines to bring pension payments for existing executives below 25%.

It is one of the first warnings on an IVIS company report due to executive pension payment breaches this year.

ShareSoc has issued its own guidelines to shareholders, recommending they vote against the bank’s latest remuneration report at the AGM on 26 April. “RBS should listen to what is being said and act,” ShareSoc said.

It also raised concerns over gender discrepancies, noting the resulting 25% difference in pension payment rates between Murray and McEwan.

RBS is preparing for a year of shareholder consultations over its remuneration policy, which will provide fresh guidelines for executive pay covering the three years from 2020.

The bank told the Guardian it doesn’t plan to change McEwan’s pension payments in the interim but has not yet committed to bringing his chief executive’s contributions in line with the rest of the workforce through the fresh pay policy.

HSBC made headlines earlier this month for making a U-turn on its pension policy, cutting its chief executive, John Flint’s, pension payments from £372,000 to £124,000, a reduction of 30%, amid growing investor pressure.

A number of companies are reviewing their pension policies but nearly half of FTSE 100 firms are still in breach of the IA’s guidelines.