Mr McCreevy's assertion that nurses are "claim jumping" the rest of the public service underlines the almost petrified state that public service pay relativities have reached.
Established by the Department of Finance in the 1960s to simplify public sector pay bargaining, they have developed a life of their own. The imposition of national pay agreements since 1987 has aggravated the problem.
Historically, nurses have done better than other "marker" grades in the public service, but not outrageously so given their low base compared with groups such as teachers.
Since 1978, for instance, wages for nurses in the basic staff nurse grade have increased by 471 per cent, while gardai have achieved increases worth 439 per cent and teachers have achieved pay increases of only 404 per cent.
However, as teachers began from a higher base, the top of their basic salary scale today is £29,310 a year, compared with £22,339 for a staff nurse and £23,245 for a garda. Clerical assistants, who scored the highest percentage pay rise in the public service after nurses - at 455 per cent - have a basic scale maximum of only £17,153. The latter are now the main marker grade for lower grades in the public sector. They have received increases worth 315 per cent since 1978, which brings their basic pay maximum to £17,432. The marker grade immediately above them are executive officers, who have received pay increases worth only 295 per cent since 1978. However, their maximum is £22,192.
Prison officers, whose pay is linked closely to that of nurses and gardai, have received pay increases of 388 per cent since 1978. This brings the top of their maximum scale to £21,926.
However, that is not the full picture. Nurses take only 13 years to reach the top of their scale, while a garda takes 19 years and a teacher 23.
The rigidity of relativities pays little regard to changes in the nature of professions. For instance, the engineering and accountancy grades in the public service once occupied a lofty perch in isolation as "graduate" professions. But now nurses are becoming graduates and groups such as social workers and teachers have achieved that status.
Even within professions the rigidity of public service relativities creates problems. For instance, probation and welfare officers working for the Department of Justice earn more than social workers in the health boards, who have exactly the same professional background and qualifications.
But probation officers have a longer pay scale. They start at £15,309 and it takes 13 years to reach the top of the scale at £30,046. Social workers start at £19,051 and take only nine years to reach the top of the scale, which is £25,564.
The traditional career pattern is for graduates to begin in the health services and end up in Justice. Again, the culprit is relativities.
