Working fathers earn a 'daddy bonus' of 22% more than their childless counterparts, with dads who have two or more children benefiting most from higher pay.
The Pay and Parenthood report which studied finances of full-time workers aged 42 found wage inequality in women was dependent on age – with women who had their first child under 33 earning 11% less than child-free female colleagues.
By comparison, women who had their first child later than 33 experienced a wage bonus of 12%, although in both cases women were surpassed in earnings by men, who took home 34% more than women overall, and 12% more in cases where both parties were without children.
The gender pay gap, which was described by the TUC-commissioned report as 'large', had significant links to parenthood, with women more likely to be primary carers for their children and often forced into low-paid or part-time work in order to look after the home.
It advised: "Mothers are kept out of work, or forced into part-time work, when childcare is expensive or is too inflexible to fit around working hours. The government should ensure that all parents have access to affordable, flexible and high-quality childcare, particularly for one- and two-year-olds."
In order to balance out such pay inequality, the report recommended encouraging 'a more equal distribution of caring responsibilities'. "Examples from other countries of more equitable parental leave systems, with rights to better paid leave for fathers, show that they can lead to lasting changes in how children are cared for.
"The UK should learn lessons from the countries where fathers are taking considerably more time off work to care for young children and introduce a more equitable parental leave system, which includes a dedicated 'use it or lose it' right to well-paid parental leave for fathers."
While women's lower earnings compared to men was largely down to childcare, the 'daddy bonus' could be linked to households using income as a determining factor for having more children.