This report is from this week’s CNBC’s UK Exchange newsletter. Each Wednesday, Ian King brings you expert insights on the most important business stories from the U.K. and other key developments you won’t want to miss. Like what you see? You can subscribe here.

Few institutions in Britain over the last decade and a half have avoided losing public confidence. Parliament, the Royal Family, the National Health Service, the BBC, the Church of England, the police service and the media have all been rocked by scandals.

One institution that has remained largely above criticism, though, is the Office for Budget Responsibility. This non-departmental public body, answerable to the House of Commons Treasury Select Committee, has by and large come through the last 15 years with its reputation intact.

But now things are changing and, for the first time in its existence, the OBR is under fire like never before.

First, some history. The OBR was born in May 2010 when the coalition government formed by the center-right Conservatives and the centrist Liberal Democrats succeeded Gordon Brown’s Labour government.