Political parites have criticised a European Court of Justice ruling yesterday that women can be paid less than men on the basis of length of service.
The ECJ landmark ruling found that length of service is a legitimate criterion to award higher pay rates to certain workers - even if women have to take time off to bring up children.
The court also ruled that employers do not have to justify on a case-by-case basis their pay structures based on the length of service.
Fine Gael's Seanad equality spokeswoman, Senator Sheila Terry, said the ruling discriminates against women and is a blow for equality.
"This ruling when enforced will discriminate against women in the workplace and flies in the face of all the progress that has been achieved in the past 30 years in the equality area," she said.
She said the ECJ had taken a "very narrow and discriminatory view".
Labour Party spokeswoman on children, Senator Kathleen O'Meara, described the ruling as "the legalisation and imposition of a biological penalty on any woman who takes leave of absence from work to have or tend for children.
"This ruling penalises women for having children. It sets the entire equal pay movement and the struggle for equal rights for women back many years. "Moreover the Irish Government must account for the stance it took and the representations it made to the ECJ opposing the British woman who was at the centre of the case."
In the specific case, the court rejected a claim by British health inspector Bernadette Cadman, who said her employer unjustifiably paid her male colleagues on the same grade more only because they had worked more years.
Ms Cadman argued length of service often depended on domestic circumstances such as pregnancy and employers must provide special justification for paying men more than women when they hold the same post.
She took the case in 2001 when she discovered that four male colleagues were paid between €6,000 and €13,350 more than her on the basis that they had longer service with the British Health and Safety Executive.
The court rejected her argument, finding that experience acquired by a worker that enabled them to perform duties better was a legitimate objective of a pay policy.