"This is a way for Senator Rubio and the Republican party to get credit for caring about women and families without truly investing in a way to address a major problem," said Andrea Flynn, a fellow at The Roosevelt Institute.
Knightley, who became a mother in 2015, said paternity and maternity leave should be equal.
It seems discrimination by some employers towards mothers-to-be is getting worse.
The Women and Equalities Committee urges for German-style regulation.
The clinic will open at the Royal London Hospital in July.