"In my opinion, there has been no political will to do anything about this," Mr Mullen said.
His unambiguous remarks were echoed this week by the Scottish Parent Teacher Council in its comments on Labour's education manifesto. Headteachers and fellow professionals "can be fed up with 'bad' colleagues, just as much as parents and students," the council states.
It believes the General Teaching Council, dominated by the Educational Institute of Scotland, would be reluctant to take on the job.
Mr Mullen, in a valedictory address, said that in every secondary one or two teachers were "shortchanging" pupils. A recent case he dealt with involved hours of management time and a file weighing 3.5 kilos.
"We have got disciplinary procedures and all the rest of it, but how many teachers have actually been removed?" Mr Mullen said later "You can follow the process on but there is no end to it. Although there is a facility, it is remarkable not one teacher has been dismissed for wilful incompetence."
He called for better detection of potentially inadequate teachers during initial training and probation. Evidence about classroom performance could be collected through departmental appraisal.
Mr Mullen's views are similar to those in Labour education manifesto and followed a speech by Raymond Robertson, the Education Minister, about the need to bolster teacher appraisal. Mr Robertson suggested he would bring in regulations after a survey showed only "one or two" areas on target.
The Government had hoped to see every teacher appraised at least once by the end of this session but the figures show only 30-40 per cent will have gone through the process. Dumfries and Galloway has made most progress.
Mr Robertson said: "The non-statutory approach we have adopted thus far has perhaps lulled some teachers or education authorities into assuming that the Government is not really interested in seeing appraisal fully implemented. This would be a wholly incorrect assumption." Appraisal is mandatory south of the border.
He was "frankly amazed" that teachers harboured fundamental reservations. "Teachers have nothing to fear and everything to gain. We have to set the place of individual teacher appraisal firmly within the staff development context. Appraisal must contain a performance review opportunity, which should include classroom practice, a look forward at possible development needs and a chance for teachers to offer views on the operation of school policies."
But Tony Finn, head of St Andrew's High, Kirkcaldy and a member of the National Co-ordinating Committee for Staff Development, warned against enforcing appraisal in the present climate of cutbacks and rapid change.
Mr Finn said: "As teachers in many parts of the country come to terms with the advantages of appraisal, it would be singularly imprudent to make appraisal mandatory. It would not be seen as a constructive sign in staffrooms and education authorities."
Tony Gavin, of St Margaret's Academy in Livingston, the incoming president of the Catholic heads, later said the type of appraisal system backed by the Government was not positive enough in staff development terms when budgets were being cut and opportunities reduced.