The singer, who looked after his mum since the age of 12, says there is a "silent army of young people" who need help caring for relatives.
A new has been produced for carers of elderly or sick relatives to help them juggle tasks.
The number of unpaid carers in England and Wales has risen to 5.8 million, according to the Office for National Statistics (ONS).
Carers save the UK "more than the NHS budget" by looking after a sick relative or friend for free and deserve some sort of Government recognition, Nick Clegg has said.
The Liberal Democrats are promising a "no strings attached bonus" of £250 every year to carers if they get into power at the next election.
– Nick Clegg
It is estimated that six in ten of us will at some point in our lives find ourselves caring for someone else - an elderly relative, a sick child, a friend who needs our support.
Obviously this makes a massive difference to the people being cared for - but Carers UK calculated that it saves us a whopping £119 billion every year - more than the entire NHS budget.
These are people who deserve our support even in these straitened times, which is why the Liberal Democrat manifesto will include a Carer's Bonus to give them a little extra help.
Around one million carers would be given an annual £250 bonus if they are looking after a sick relative, the Liberal Democrats have said.
Party leader Nick Clegg wants to double the carers allowance from £125 by the year 2020 and will make the pledge in the Lib Dem's manifesto for the 2015 election.
Mr Clegg said the extra money was a recognition of the "superhuman" work done by the "hidden army of carers".
A spokesman for the party claimed there would be a "fully costed manifesto" of the pledge, however critics of the scheme have argued the Lib Dems have not provided any details of how they would raise £280 million needed.
Carers should be routinely screened for depression and mental health problems, doctors' leaders said today.
The Royal College of General Practitioners (RCGP) warned that carers often "neglect" their own healthcare, and found that around 40 percent experience depression or psychological problems.
Dr Clare Gerada, RCGP chairman, said: "Carers often neglect their own healthcare needs and in many cases it is only a matter of time before they themselves become ill.
"They are at risk physically and emotionally with stress-related illnesses, but it can be hard for them to admit that they are struggling."
The RCGP has drawn up a nine-point checklist as part of new online guidance that also includes appointing a carers' "champion" in all GP surgeries.