Opposition Leader Tony Abbott has reignited the sexism debate by saying his paid parental leave scheme is about encouraging women "of calibre" to have children.

Mr Abbott is facing a backlash from coalition colleagues over the parental leave policy, with three Liberal MPs publicly condemning it as economically irresponsible and calling for it to be dumped.

The policy entitles a woman to her full wage at 26 weeks, capped at $150,000, including superannuation contributions and is funded through a levy on about 3000 big businesses.

Calling for unity and defending the policy, Mr Abbott told reporters on Tuesday that the women it would benefit were "in the prime of life and they should be able not just to have kids but to have careers".

"We do not educate women to higher degree level to deny them a career," Mr Abbott said.

"If we want women of that calibre to have families, and we should, well we have to give them a fair dinkum chance to do so. That is what this scheme of paid parental leave is all about."

Health Minister Tanya Plibersek said Mr Abbott's comments were an insight into "his lack of respect for low income workers and women in particular".

"Who exactly does Mr Abbott think are women of calibre? What does he think about women who are child care workers, nurses and community sector workers?" Ms Plibersek said.

"Are they of lower calibre than women who are law firm partners?"

Finance Minister Penny Wong took to Twitter to remark: "Am wondering who Abbott thinks the women not of calibre are? A woman's calibre is not determined by what she earns."