The latest release of documents about Peter Mandelson’s appointment as US ambassador reveals worrying direction of travel among backbench Labour MPs as they lobby for more tax rises in face of highest tax burden in decades.

Tax and benefits were addressed in one WhatsApp exchange between Mandelson and Pat McFadden, who was minister for intergovernmental relations, but is now secretary of state for work and pensions, responsible for oversight of benefit reform.

At the time of the message thread, the government was facing a major showdown with the parliamentary Labour party (PLP) about plans to cut benefit payments for new claimants, an argument which they eventually lost.