New laws to combat underage drinking will be unveiled later by the Government. The measures are part of a cross-Whitehall alcohol action plan. Under the new initiative anybody looking under 21 will be challenged by bars and off-licences to prove they are an adult before being sold alcohol. Vendors will also be subjected to a "two-strikes" rule on selling booze to children as ministers seek to curb binge-drinking among teenagers. Parents, meanwhile, are to be presented with new guidance about what age children should be allowed to drink, how much and under what kind of parental supervision. Other moves, include criminalising under-18s who refuse to stop drinking in the streets and court orders requiring their parents to step in. The strategy comes amid heightened concern among voters about anti-social behaviour and alcohol abuse among younger people. Children and Schools Secretary Ed Balls said: "Tougher enforcement powers are needed to tackle under-age binge drinking but enforcement measures alone are not the solution. "We need a culture change about drinking, with everyone from parents, the alcohol industry and young people all taking more responsibility. "We need to fundamentally influence young people's behaviour and attitudes towards alcohol. "This will involve talking to young people themselves but, crucially parents tell us they want better, clearer information as they bring up their children."