Spending on the NHS should be paid for by a dedicated tax marked on every payslip, former health minister Norman Lamb will tell the Liberal Democrat conference today.
Under the plan, overall taxes would not be increased as the new levy would be offset by deductions to income tax or national insurance.
But local areas should be able to raise additional money to top up spending on specific services, Mr Lamb will argue.
And creating a separate NHS tax would allow it to be increased in future without changing headline rates of other taxes. Party sources pointed to polling which indicated this could be acceptable to voters.
He will say: "I am very interested in the idea of a dedicated NHS and care contribution - separating it out from the rest of taxation, clearly identified on your pay slip.
"And I am really interested in the idea of the right for local areas to raise additional funds for the NHS and care if they choose.
"Why can't my county of Norfolk decide to spend more on vital services for older people, to improve cancer services or for mental health if it chooses?"
Creating a separate tax is not an official Liberal Democrat policy and will not be debated or adopted by members at the Bournemouth conference.
Mr Lamb will warn the health service faces collapse without an emergency injection of extra money, citing his experience as a coalition minister in the Department of Health.
Plans are in place to cover £30 billion of additional spending - via £10 billion of new money and £20 billion of efficiency savings - to maintain services at current levels in 2020.
The Local Government Association has estimated £5 billion more is need to cover a black hole in social care and higher pay bills because of the increased minimum wage.
And Mr Lamb will warn even more money is needed on top.
He will say: "I've been in the department. I have seen the books and I am deeply concerned.
"If we carry on regardless, the system will crash. This is not the time for long grass. This is the time for action."
The former care minister plans to begin a "national conversation" on possible solutions to the funding crisis and will promise his activists to avoid party politics by including Labour and the Conservatives.
The idea of a new NHS tax was not pushed for by Mr Lamb in government.
Mr Lamb will say: "I argued for the same approach on care before the 2010 election. I will keep making this case. I will not give up until this case is won.
"So today, I am starting a national conversation. We have to talk about the emerging crisis in care.
"I will travel the country meeting with people, patients, carers, local authorities, charities, health leaders, doctors and nurses, public, private and voluntary sector. We will invite contributions from think-tanks, from academics and from trade unions.
"We will confront both the need for more resources and for change."
Elsewhere, emotional tributes will be paid to the late former leader Charles Kennedy.
Mr Kennedy, who died in June, led the party from 1999 to 2006 and to their greatest electoral success.
A tribute film will be shown and there will be speeches from senior party figures.
Leader Tim Farron will pay a warm tribute in his main leader's address on Wednesday.