An additional £2billion each year is expected to be allocated for mental health crisis services in the upcoming budget announcement.
Philip Hammond will use the Budget, to be outlined on Monday, to set out the start of a long-term plan to achieve "parity of care" between physical and mental health.
This extra money is set to pay for the provision of "comprehensive" mental health support in every major NHS A&E department.
It is hoped this would ensure anyone experiencing a mental health crisis can get rapid specialist help.
The additional funding forms part of the extra £20 billion-a-year by 2023 for the NHS in England which Theresa May announced in June.
This announcement was welcomed by Paul Farmer, chief executive of the mental health charity Mind.
Stating services had been underfunded for decades, he said: “This commitment ahead of the long-term plan indicates that mental health is rightly high on the Government's agenda, and has the potential to improve access to care, once detailed plans are clear.”
However, he expressed concern the Government had yet to provide assurances no claimants receiving benefits due their mental health making it difficult to work would lose income in the transition to Universal Credit.
"This has not yet been forthcoming," he said.
"If the Government is really intent on prioritising the nation's mental health, it needs to guarantee nobody with mental health problems will be left without their income as a result of moving to Universal Credit."
Shadow health minister Barbara Keeley expressed scepticism about the promise of extra funding.
She said: "If this announcement is simply money that's already been promised, it will do little to relieve the severe pressures on mental health services that have built up because of this Tory Government's relentless underfunding of the NHS.
"People with mental health conditions cannot afford to wait five years for meaningful action from this Government: too many are already waiting many months to access the treatment."
Officials say the new funding will be backed up with more mental health ambulances along with the establishment of dedicated mental health teams in schools.
Callers to NHS 111 will be directed to support services 24 hours a day while there will be greater access to services in the community.
This will include "crisis cafes" where people can get help without going to emergency departments.
