The Government is being urged to put family at the centre of policy-making, and will be told by the Children’s Commissioner for England that “investing in family is the single greatest investment you can make”.

Dame Rachel de Souza has urged the incoming Conservative leader’s administration to “prioritise” putting families “at the heart” of policy-making, as she warned in a new Government-commissioned report that gaps in official data fail to capture families as they see themselves.

The report says that the Government should be “unashamed” about wanting to support and strengthen families.

But it also warns that to do this “will require an updated understanding, based on the Family Review, of what is important about families. Government should pursue a positive vision for family life, with a clear objective for all families to be loving, supportive and prosperous”.

We know that if children have supportive families, they are more likely to succeed later on in life. They are more likely to have healthy relationships and happy lives

It added: “This will require changes to the way public services are delivered, to ensure that all families can get the kind of help they need to reach this goal. But it will also require broader changes to public policy.”

For instance, the report warns of “significant variation” in access to services for parents around the country.

The first part of the study into family life reveals how family structure has changed over the past 20 years, with fewer married couples, more cohabiting couples and fewer ‘traditional’ nuclear family units.

Some 44% of children born at the start of the century did not grow up in a “nuclear” family for their full childhood, compared with 21% of children born in 1970, it found.

But the proportion of single-parent families has not changed much – with 23% of families headed by a lone parent, and around 90% of lone parents women.

Some 63% of families are married couples with children, while 14% are co-habiting couples.

According to the review, family has a “protective effect” that insulates families from challenging times.

Dame Rachel’s review also cites data that getting on well with either of your parents aged 13 is associated with 2% higher wages aged 25.

It also suggests that spending time with family is associated with higher wellbeing, with data suggesting that in families that eat dinner together at least six days a week, 75% of parents were happy with their life – compared with 70% overall.

In a speech on Thursday, Dame Rachel will say that children and parents alike believe “family is everything”.

Society must not be “afraid” or “squeamish” to talk about family, she will say at the event hosted by the Policy Exchange, adding that now is the moment to “gear change” and give families the priority they afford themselves.

She will say: “Investing in family is the single greatest investment you can make.

“If we do it right it is self-sustaining unit and there to catch us when we fall, and if you are part of a strong family, you cast your net wider to catch others.

“I am calling on everyone to put family centre stage of their agenda.

“If we get this right at a critical moment for families across the country, we will benefit generations to come and change children’s lives.”

The second part of the review will be published in the months to come and is expected to look at how services can be designed to support families’ needs.

More data will also be obtained through a new survey for children to complete in schools.

The review reports that the amount of time fathers spent on unpaid childcare doubled from 47 minutes a day in 2014-15 to 90 minutes a day during lockdown, before dropping back to 56 minutes this year.

Around 25% of parents also reported that their relationship with their children had become better during lockdown, according to Dame Rachel’s study.