Sarah Palin, John McCain’s Republican running mate in the US presidential race, on Monday revealed that her 17-year-old daughter, Bristol, was pregnant and would marry the father of the child.

The McCain campaign said the decision to go public was prompted by the need to quash a swirl of internet rumours speculating on whether Bristol was in fact the real mother of Mrs Palin’s most recent child, Trig, to whom she gave birth in April.