The union representing senior civil servants has described Government proposals to address performance management as "totally unworkable."

The Government wants to have a stricter measurement of performance, as research has shown statistically unusually high performance ratings among Irish public servants.

Addressing the annual conference of the Association of Higher Civil and Public Servants, union chairman Peadar Carpenter said the new ratings system would introduce what he called "forced distribution”.

This means a certain percentage of staff would have to be given low ratings to meet an expected statistic distribution, regardless of their actual performance.

A low grade could deny them increments and access to promotion.

He asked what would happen if a manager told a member of staff that they deserved a higher mark, but had to be given a lower one to fit in with the scheme.

He also said the old scheme had given managers scope to reward staff when morale was low.

He said the scheme had the potential to tie managers up in endless discussions and arguments about marks - and he questioned the whole logic behind it.

He warned that many public servants were suffering from what he called "survivor stress" from trying to do extra work due to what he called an exodus from the public service - and said that if additional resources were not allocated, the system could seize up.

He also criticised Government proposals to amend sick leave entitlements.

Mr Carpenter described the current system of politicians' expenses as grubby and unbecoming of those who would set themselves up as acting in the national interests.

He said no public representative should have access to funds for unspecified purposes, and that all expenses should be paid on a strictly vouched basis only.

However, he praised former President Mary McAleese for handing back unspent allowances worth €500,000.