Mitt Romney makes 'birther' dig on campaign stump

Republican presidential candidate Mitt Romney has referred at a campaign rally to a discredited theory that President Barack Obama was not born in the US.

Speaking near his childhood home in Michigan, Mr Romney joked that no-one had asked to see his birth certificate, referring to a debunked conspiracy theory that Mr Obama, whose father was from Kenya, was not born in the US and is not eligible to be president.

The Obama campaign responded swiftly, claiming Mr Romney had "embraced" the most extreme conservative claims.