The five-question online survey aims to "spark a national conversation" to help create "lasting change for generations to come", Kensington Palace said.

Catherine is marking its launch with visits to a museum in Birmingham, a nursery in London and a baby sensory class in Cardiff.

The NSPCC said the project would be a "vital source of information".

In the survey, called Five Big Questions, participants are asked for their opinion on what influences development and what period of childhood is most important for children's happiness.

On Tuesday the duchess visited Thinktank, a science museum in Birmingham.

She was shown around an interactive mini city inside the museum and spoke to parents and carers about her survey.

Business as usual

Analysis by Daniela Relph, BBC royal correspondent

It is stating the obvious to say it has been a difficult week for the Royal Family.

But with Harry and Meghan now back in Canada and big decisions made about their future there is a sense of returning to business as usual... at least for now.

For the Duchess of Cambridge that means an even sharper focus on one particular area - the problems of early childhood.

Royal engagements can cover a vast number of areas but for the duchess an increasing amount of her work is targeted at early years.

This new survey will ultimately help provide important data for all those working in the area of early years, and will also inform the kind of work the Duchess of Cambridge gets involved with in the future.

Those who have worked with her in this area say she is totally committed and isn't just a figurehead.

She has built up an expertise and wants to prevent the same problems affecting the same families generation after generation.

On Wednesday morning Catherine will join parents as they drop off their children at a nursery in Southwark, south London, before helping to serve breakfast to the children.

She will attend a baby sensory class at the Ely and Caerau Children's Centre in Cardiff to hear about the support parents receive there.

Catherine and her husband, the Duke of Cambridge, have three children - six-year-old Prince George, four-year-old Princess Charlotte, and 21-month-old Prince Louis.

Princess Charlotte and Prince George both attend the lower school at Thomas's Battersea, while Prince Louis has not yet started nursery.

The Royal Foundation website says Catherine believes "many of society's greatest social and health challenges" could be "mitigated or entirely avoided" if young children are given "the right support".

Kate Stanley, from the NSPCC, says the duchess's survey will "provide fascinating insight into how we think about the early years and it will be a vital source of information for the sector".

Ipsos Mori, which is conducting the survey on behalf of the Royal Foundation, said it was a "fantastic way for the British public to share their views".

The company's Kelly Beaver added: "Whilst many studies have been conducted to generate evidence of the importance of the early years, there is a real lack of evidence to understand whether this is understood by the British public."

The survey will be open until 21 February.

The 'five big questions'

1. What do you believe is most important for children growing up in the UK today to live a happy adult life? Rank from most important to least important:

Good physical and mental health
Good friendships and relationships
Access to opportunities
Access to a good education
2. Which of these statements is closest to your opinion?

It is primarily the responsibility of parents to give children aged 0-5 the best chance of health and happiness
It is primarily the responsibility of others in society to give children aged 0-5 the best chance of health and happiness
It is the shared responsibility of parents and others in society to give children aged 0-5 the best chance of health and happiness

Don't know

3. How much do you agree or disagree with this statement? The mental health and wellbeing of parents and carers has a great impact on the development of their child(ren)

Strongly agree
Tend to agree
Neither agree nor disagree
Tend to disagree
Strongly disagree

4. Which of the following is closest to your opinion of what influences how children develop from the start of pregnancy to age five?

Mostly the traits a child is born with (i.e. nature)
Mostly the experiences of a child in the early years (i.e. nurture)
Both nature and nurture equally
Don't know

5. Which period of a child and young person's life do you think is the most important for health and happiness in adulthood?

Start of pregnancy to five years
5-11 years (primary school)
11-16 years (secondary school)
16-18 years (further education)
18-24 years (young adulthood)
Don't know
All equally important