British leaders united Friday to defend the country's state-funded National Health Service, as it comes under fire in an increasingly heated debate in the United States over healthcare reform. Prime Minister Gordon Brown and opposition Conservative leader David Cameron both supported a campaign on the micro-blogging website Twitter in support of the NHS. "I think people will be shocked by the attacks being launched on the NHS in the US," said Brown's business minister Peter Mandelson. Cameron -- whose severely-disabled six-year-old son Ivan died in February -- paid tribute to how the NHS helped his family.