Bringing mental health services in line with physical health services will take "a generation", the health secretary has admitted, despite the government having promised to achieve it by 2020.
It comes as Philip Hammond, the Chancellor, prepares to deliver a Budget that will include a cash boost for mental health services.
£2bn of the government's £20bn of additional funding for the NHS will be used to provide specialist mental health support in every A&E department, more specialist ambulances and mental health teams in schools.
But Mr Hancock's admission will prompt concerns over the pace of improvements to services, which mental health professionals say are at breaking point.
The Coalition government committed to achieving "parity of esteem" by 2020 and enshrined the aim in law in the 2012 Health and Social Care Act.
But asked when he expected the promise to be met, the health secretary said it was "the work of a generation" and would not necessarily be achieved within the NHS's next ten-year plan.
He told BBC Radio 4's Today: "This plan is over a ten year period. The work to put mental health services on the same footing as physical health services is the work of a generation."
Asked about figures showing that, by 2020/21, two-thirds of children will not have access to the mental health services they need, he said: "I think that if we had those sort of figures for physical illnesses then people would rightly be up in arms and so we're going to tackle that, absolutely."
Mr Hancock has previously admitted that there remains a significant gap between mental health and physical health services, saying: “It’s still way off where we need to be.”
He told Today that the increased funding for the NHS would not be impacted by a no-deal Brexit, despite Mr Hammond having warned that his plans will have to be redrawn if Britain crashes out of the EU.
He said: "The extra £20 billion for the NHS is coming. We'll see it in the figures today and that is irrespective of the deal that we get on Brexit.
"Now, I think that we'll get a good deal on Brexit and there's evidence that a good deal will lead to more money in the economy."
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies