Soaring childcare costs mean full-time work is hardly worthwhile for a growing number of "second earners" in middle and low-income families.

In the most extreme case – where a second earner takes on a full-time job at the minimum wage – a couple who use childcare could be left just £4 a week better off with two incomes than they would be with one, according to a study.

The report, Counting the Costs of Childcare, by the politically independent Resolution Foundation, found childcare costs are also eroding incentives to work for those higher up the income scale. Vidhya Alakeson, deputy chief executive of the Foundation and joint author of the report, said: "This is a concern because increasing female employment is one of the key routes through which family living standards have increased. We need major change in our childcare system to ensure that work is always worthwhile."