Aviva, the insurer, which employs 16,000 people in the UK, will offer all employees 26 weeks of leave at full basic pay after they have a child. 

The rights apply to both men and women regardless of how they become a parent, whether through birth, adoption or surrogacy. 

The law requires companies to give all employees six weeks of maternity leave paid at 90 per cent of average earnings before tax, followed by 33 weeks paid at £140.98 per week or 90 per cent of earnings, whichever is lower. 

New mothers are entited to a year off work but after 39 weeks employers can cease to pay the employee anything. 

Under new shared parental leave laws which came into effect in 2015, parents can split their 52 weeks of leave and receive payment for 39 of those weeks at the same rate of £140.98 a week.

Aviva's policy means that parents do not have to share their leave, and couples where both parents work for the company each have their own equal allowance. 

It applies for all full time and part-time employees who become a parent after November 19 in the UK, Ireland, France, Singapore and Canada. The company employs 30,000 people worldwide. 

 Sarah Morris, chief people officer at Aviva, said: “We think this is one of the most ground-breaking, family-friendly policies offered by any employer. 

"It’s time to equalise parental leave and create a level playing field for men and women who want to take time out from their career to spend with their family."

Ms Morris is on the steering committee of the 30% Club, which campaigns for greater representation of women on the boards of FTSE 100 companies.