Owen Smith has questioned Labour leader Jeremy Corbyn's patriotism, suggesting it is not "part of his make-up".
The leadership challenger said Corbyn's "metropolitan" politics were at odds with Labour traditions about national identity in England, Scotland and Wales.
The former shadow cabinet minister suggested he would be prepared to offer his rival a job in his own shadow cabinet if he won the contest, having previously suggested Corbyn could become Labour's president or chairman - an idea the incumbent leader rejected.
Last week Corbyn was totally incompetent. Now Smith would give him a job in the shadow cabinet. Its make your mind up time guys!
-- Aaron Bastani (@AaronBastani) July 25, 2016
Smith - who said he would meet the Nato target of spending 2% of GDP on defence, renew Trident and be prepared to push the button to launch a nuclear strike if he was in No 10 - said: "One of the weaknesses we have had recently is that people worry that Labour isn't serious about security, that it is a lesser issue for Jeremy.
"I'm not sure that's right, but he has certainly got a different perspective on some of those things - on patriotism if you like; and on security, on defence I think I have got a more traditional Labour perspective on that - an old-fashioned Labour perspective, if you like."
He added: "I think Jeremy, to be honest, doesn't really understand sometimes the way in which people have a very strong, perhaps socially conservative... sense of place, sense of where they are from.
"I am not sure I've heard him talking much about Scotland and identity or about Wales and identity or indeed about England and identity. I suspect that Jeremy has got a rather more metropolitan sense of that and that's not one I think is central to the Labour tradition."
Asked if he was calling Corbyn unpatriotic, Smith told BBC2´s Newsnight: "I am saying that I think it is something that is not core to his set of beliefs. He has got a set of liberal perspectives and left perspectives on things and nationhood and nationalism and patriotism aren't really part of his make-up."
Corbyn's patriotism has been questioned before - including after he refused to sing the national anthem at a Battle of Britain memorial service in St Paul's Cathedral.