The leading US senator Elizabeth Warren has called for urgent answers from Barclays over what she claimed was its “apparent failure to meaningfully investigate” ties between the bank’s former boss, Jes Staley, and the late sex offender Jeffrey Epstein.

In a letter sent privately to Barclays’s chair, Nigel Higgins, and seen by the Guardian, Warren – the most senior Democrat on the US senate banking committee – said it was “deeply unclear how Barclays, supposedly investigating Staley’s connection to Epstein, failed to uncover this decades-long relationship”.