ROYAL Bank of Scotland (RBS) has offered to pay millions of pounds more to shareholders who are in the process of suing it over the 2008 rights issue that preceded its taxpayer bail-out.

The bank’s lawyers are understood to have proposed an increased per-share settlement of 43.5p with members of the RBoS Shareholder Action Group – the last claimants to settle over its £12 billion cash call.

It is marginally higher than the 41.5p-per share agreed with four other claimant groups, and would cost RBS millions of pounds.

The move comes as a new sustainability index of Europe’s 40 biggest banks launches, with RBS maintaining its E- rating at the bottom of the table.

Standard Ethics (SE) gave RBS its lowest rating in its British table which now transfers to the European list, effective from close of business on Friday.

The top three banks, which all have EE+ ratings, are Paris-based BNP Paribas, the Nordic institution Nordea Bank AB and Unicredit Spa, which is headquartered in Rome. Five other British banks are included in the listings – HSBC, in sixth place, Allied Irish (17), Bank of Ireland (20), Lloyds (25) and Barclays (29).

Ratings are still pending for Standard Chartered and Clydesdale and Yorkshire Banking Group.

Filippo Cecchi, from SE, said HBOS was not included because the selection criteria were about asset and market capital size and did not measure up to the international competition.

Of the new table, he said: “EE+ tells us that the banks are more compliant with the indications on corporate governance and corporate social responsibility coming from the international bodies such as the Organisation for Economic Cooperation and Development (OECD), the UN and the EU.

“Conversely, E- tells that the bank is distant.”

When SE first rated RBS last May, the agency said it had considered its stormy, recent history from the time of its £445.5bn government bail-out through to its multi-million dollar pay-outs to US regulators for its misbehaviour there.