France is under mounting pressure to help finance Ukraine by using €18bn of Russian sovereign assets largely immobilised at private banks whose identities Paris has kept under wraps for more than two years.

To the irritation of some other European capitals, France has withheld any details on the institutions holding the Russian state funds and how any interest accrued is used, claiming it is an issue of client confidentiality.

The holdings have come under renewed scrutiny as the European Commission pursues a plan for a “reparations loan” to Ukraine backed by Russian central bank assets under sanctions. The latest proposal aims to use funds frozen across the EU and not just the main €185bn holding at Euroclear, the Brussels-based central securities depository.