The Liberal Democrats plan to give carers looking after elderly, ill or disabled loved ones a "bonus" of £250 which they can spend on whatever they like.
Party leader Nick Clegg said it was part of a package to reward the "unsung heroes of British society".
He added the party would also consult with businesses on giving an entitlement of five days' paid "care leave" a year.
Other proposals include:
- Increasing the amount people can earn without losing their carers allowance from £110 a week to £150
- Introducing a 'carer's passport' to offer privileges such as free hospital parking through to free cinema tickets, meals and gym discounts
The bonus, which would be paid for by a levy on tobacco firms' profits, would start at £125 in 2017/18 and increase to £250 by 2020.
Clegg said: "Currently one in every eight adults across the UK are carers supporting a family member who is older, disabled or seriously ill.
"They are the unsung heroes of British society, quietly going about helping their loved ones without seeking favour or thanks for their kindness.
"But more needs to be done to help carers get the support they deserve.
"Whilst the Care Act introduced by the Liberal Democrats ensured £400 million was given to the NHS dedicated to helping carers take much-needed breaks, we want to go much further.
"Our new £150 million Carer's Package will ensure society pays back the service that carers give to their loved ones and the community, easing the pressure they are under, and providing the support needed to live happier, more fulfilling lives."