Bill Clinton took centre stage at the Democratic National Convention as President Barack Obama’s nomination is placed before a party hoping that the last president to preside over sustained growth can help propel him to re-election in a sputtering economy.

Democrats launched President Barack Obama on his uncertain bid for re-election as they opened their national convention.

US President Barack Obama last night ampooned the Republican National Convention as better suited to an era of black-and-white television as he declared that Mitt Romney “did not offer a single new idea” to fix the economy.