The two-time Oscar winning actor appeared on the same stage as opposition leader David Cameron to support the National Citizen Service.
"You may think to yourself 'what the hell is he doing here, why is he here?'," Caine said after being introduced by Cameron at a news conference. "I'm here because I'm a representative of all those youngsters that have been forgotten in this country."
A supporter of Margaret Thatcher in the 1980s, Caine had been won over by former Prime Minister Tony Blair in Labour's sweep to power in 1997. But Caine has expressed anger over Labour's tax plans - the top bracket income tax rate rose to 50 percent last week - and threatened to leave the country if taxes went higher.
He said last year he would support Cameron, and arguing no party should serve more than two terms in office. The election will be held May 6.
"My view of politicians is that we elect them as servants," he said later at a visit to a London school. "For two terms they are our servants, the third term they are our masters."
Caine has for decades been one of Britain's most popular and accomplished actors, ranging from early roles in classics like "Alfie" and "Get Carter" and "The Italian Job" to contemporary parts in the high-budget Batman series. He has excelled in comedy, action and dramatic roles for more than half a century.
He has been nominated for six Academy Awards, winning the best supporting actor Oscar in 2000 for "The Cider House Rules" and in 1987 for "Hannah and Her Sisters." He received a knighthood from Queen Elizabeth II in 2000.
The program offers two-month summer social activities such as looking after the elderly. The Labour Party also has proposed a program aimed at young people.
Last April, Prime Minister Gordon Brown announced he'd include a plan to have young people carry out compulsory community service in the party's election manifesto. Under his proposal, young Britons would be expected to carry out 50 hours of volunteer work before the age of 19.
Caine said he was able to pull himself up from unfortunate circumstances - though he acknowledged times had changed. Young people need a second chance, he said.
"What I had was a loving family, a loving father and an education," he said. "And what I didn't have - I didn't have drugs and I didn't have guns.
"You have now a very, very hard core of people who we've got really to save, and that's what attracts me about this."
