Employers face an “administrative nightmare” under plans to be announced on Tuesday to give fathers the right to up to three months’ paid paternity leave, business representatives have warned.

The new right would allow mothers, who go back to work after six months, to transfer their unused six months of maternity leave to their partner. This would give fathers a statutory right to up to three months’ paid and three months’ unpaid leave, in contrast to the maximum fortnight’s paid leave they enjoy at present. Gay couples could also share maternity leave.