The Prince of Wales stood side-by-side with the three main political party leaders as he helped launch a campaign to bolster youth volunteering.
Launching Step Up to Serve at Buckingham Palace, the Prince, Prime M inister David Cameron, Lib Dem leader Nick Clegg and Labour's Ed Miliband called on more youngsters aged 10 to 20 to get involved so participation levels are doubled to more than 50% by 2020.
Charles described it as "a huge but exciting challenge", but admitted "that it may look as though we have bitten off more than we can chew".
He told nearly 200 invited guests and supporters including business leaders, education and community workers - plus Barry and Margaret Mizen, the parents of murdered schoolboy Jimmy Mizen - that youth organisations can help transform lives.
This must be a "giant, unique and collaborative effort", according to the Prince, and it will provide "many more structured, constructive and challenging and adventurous opportunities for young people".
The Mizens met the Prince the year after their 16-year-old son Jimmy was killed in Lee, south-east London, in 2008.
Jimmy died in his brother's arms after Jake Fahri hurled a glass dish at him in a bakery following a trivial row. A shard cut his throat and he bled to death.
Since Fahri's conviction in 2009, Mr and Mrs Mizen have been campaigning to end the violence in London through the Jimmy Mizen Foundation.
"I think that what today is about is not giving up on our young people," Mrs Mizen said.
"There is no politics in this. It is about our young people."
Mr Mizen said: "We have always said since the early days after Jimmy's death that the changes that we need to certain areas of our society will only come when we all take responsibility for our own actions.
"There is a part for everybody to play and for everybody to be part of improving society."
It is hoped that 1.7 million more young people aged 10 to 20 will be spurred on to make social action - defined as "practical action in the service of others" - a habit for life.
This target would add almost 90 million hours of voluntary work per year, worth almost £700 million to the UK economy. In Canada an estimated 58% of young people participate, over half of them giving more than four hours each per month.
It is hoped that a life-long culture of volunteering will be created through the campaign.
Businesses, education institutions, faith groups, youth organisations and voluntary groups across the UK are all backing the campaign.
Step Up to Serve calls for people across the UK to sign-up and volunteer at the website www.stepuptoserve.org.uk/iwill. They can also pledge a personal #iwill commitment and share it on Twitter.
The politicians joked that the next time they would be sharing a platform together would be when they are "tearing strips off each other" during the general election - but on this issue they were all united.
Mr Cameron said: "There are lots of things we disagree about but one thing we absolutely agree about is the importance of volunteering and our great charitable sector."
Mr Clegg said: "Social action, of course, brings great benefits to the communities where the projects are hosted and, of course ,it is very inspiring.
"The most galvanising thing of all is the transforming effect it seems to have in the confidence of the youngsters themselves. It is a magnificent platform for them to go on and achieve bigger and better things."
Mr Miliband praised the youngsters who would give their time to a cause. "They show what is great about our country," he said.
"They show us that there is nothing wrong in Britain that cannot be fixed by what is right in Britain."
Somali-born Naima Swaleh, 22, of Stratford, east London, said that volunteering has "made me feel more confident and realise that I can achieve anything I set my mind to."
She used to self-harm, get in to trouble at school for stealing from other people and became so desperate that she ran away from home, slept rough and has twice tried to commit suicide.
"I think I was made to help people. It has changed my life," she said.
A range of businesses, government agencies, plus firms from the voluntary and education sector have all made pledges to help the campaign.
This includes O2's pledge to give financial backing to 10,000 youth projects that could help 50,000 young people participate in youth action programmes.
They are also planning an annual celebration at The O2 to recognise and reward young people's contributions and to help youngsters turn their projects in to sustainable digital or social ventures.