Leading article: Mr Balls loses his bearings

Last summer's exams marking fiasco, in which the Sats results of thousands of pupils were either lost or delayed for months, was a particularly wretched episode in the history of the examination regime introduced by this Government. Yet no ministerial heads rolled over the debacle. Instead, it was Ken Boston, the chief executive of the Qualifications and Curriculum Authority (QCA), who fell on his sword last December, after an independent inquiry by Lord Sutherland blamed an "it'll be all right on the night" culture at the QCA for the shambles.

The political waters seemed to close over the matter. But now Mr Boston has resurfaced with some explosive testimony before the House of Commons education committee. While he does not seek to deny that the performance of the QCA was unsatisfactory, he strongly objects to the behaviour of the education department and its Secretary of State, Ed Balls, during and following the crisis.

According to Mr Boston, the remit of the Sutherland inquiry was deliberately framed by the education department to throw a "protective fence" around ministers and to put the QCA directly in the firing line.

Mr Boston also accuses the Government of unfairly presenting him as "complacent and disengaged". Claims from ministers that they requested constant updates on the situation from the QCA are dismissed as "fiction".

This row feeds into broader issues of accountability and public life. In this age of proliferating quangos and "arms length" regulators it would be unreasonable to suggest that ministers alone should be held responsible when things go wrong.

It is entirely appropriate that heads of organisation such as the QCA answer to the public when they fail, and the QCA certainly did fail under Mr Boston's leadership. There were signs that ETS Europe, the private company appointed to mark the exams, might find it difficult to deliver on its contract.

Yet, at the same time, there is something distasteful about the manner in which Mr Balls and his fellow ministers sought to dodge all responsibility for the mess. Ministers might not have been responsible for commissioning ETS to mark the scripts, but they are still deeply involved in the exams administration process. The education ministry, for instance, vetoed a proposal from Mr Boston in 2006 to move to an online marking system for national curriculum tests.

Yet the most distasteful aspect of the behaviour of ministers was their underhand attempt to portray Mr Boston as incompetent, even going so far as to refer to his supposedly lacklustre contribution at a crucial meeting to which he was never, it turns out, invited. This echoes the sort of political smearing we witnessed in Damian McBride's notorious recent email.

Mr Boston has, rightly, admitted his personal culpability for his responsibility for the unmarked exam papers. We now need a similarly contrite admission of error from Mr Balls.