The head of the Civil Service has told Guardian editor Alan Rusbridger that Richard Caseby went “beyond what I would expect of a civil servant” in a comment piece which appeared in Press Gazette last month.

Former Sun managing editor Caseby, now director of communications for the Department of Work and Pensions, wrote a comment piece for Press Gazette last month suggesting The Guardian should be "blackballed" from the Independent Press Standards Organisation press regulator.

In the piece, he cited several inaccuracies in the newspaper's coverage of welfare reform and described IPSO as the "only show in town" for press regulation.