embittering , also: imbittering

The result, many delegates say, has been a general embittering of North-South relations at the conference, with the Group of 77 pushing a number of demands the northern countries consider extreme, politicized and unacceptable.

The letters read: "I am sure you would agree the pay dispute in the fire service has gone on for long enough in such a vital public service, and a further embittering of industrial relations will do no service to the public, nor will it help the government's public services agenda.