Extending maternity leave to a year could adversely affect women's career prospects, the chief executive of the Equalities and Human Rights Commission has warned.

Nicola Brewer warned that employers would be wary of recruiting women of childbearing age or offering them promotion to more senior roles if they thought they might disappear for a year on maternity leave.

She said sharing parental leave between the mother and father would be one way of addressing the problem but the Federation of Small Businesses warned this would create even more bureaucracy.

"Transferring the leave from mum to dad will bring another employer into what is a very complex system," warned the organisation's Stephen Alambritis.

"Sometimes it's not the leave itself that we are concerned about or the pay; it's the administrative hassle of the leave."

Under laws introduced in April 2007, women can now take 52 weeks' maternity leave, and receive statutory maternity pay for 39.