"The Ashes is the biggest thing in cricket, let's not forget that, and I am one of those that cannot give a hoot about the World Cup coming up if we win the Ashes," Swann said.
"That is why I want the England Test team to be in the best possible shape, and I believe that is with Alastair Cook as a confident leader who is still brimming with the feelings of that India Test victory. I think that is going to be chipped away this winter, when I can't see them winning many games," the former off-spinner said on BBC Radio 5 Live.
Whatever decisions are made, Swann believes it is imperative to England's Ashes chances that Cook is not scarred by what he regards as inevitable one-day failures this winter.
"The whole reason I didn't want Cooky playing in this series is that I knew the brand of cricket England were going to play. I knew it was not going to be enough and I don't want him involved in all this turmoil when he had done so well to boost his stock levels after the Test series," he said.
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Swann and Cook were close as England team-mates, but their relationship has been strained in recent weeks after Swann's retirement and his suggestions that Cook should not be playing one-day international cricket.
Cook responded by referring to Swann as a "so-called friend", although they have tried unsuccessfully to contact each other by phone since.
Under Cook, England have lost five successive one-day series, including the present one against India, having fought back to win the Test series 3-1.