It is claimed there was an incident in a bar in Perth during England’s pre-series tour match against Cricket Australia.
The ECB are yet to comment on the allegations.
Sky News Australia tweeted: “The ECB is investigating reports English batsman Jonny Bairstow headbutted Australian batsman Cameron Bancroft in Perth earlier this month.”
The police were not involved, while Bancroft did not either provoke or retaliate in the incident.
The allegations come to light as England bowler Ben Stokes misses the tour following an incident outside a bar in Bristol last month.

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England decided against an alcohol curfew for the tour, with head coach Trevor Bayliss saying: “The players sat down and had a chat.
“They are the ones who have come up with this.
“There are no set curfews, they are just sensible rulings.
“To me, it’s what we should have been sticking to anyway as players or people around a professional set-up.
ENGLAND ON VERGE OF ASHES FIRST TEST DEFEAT
“Not drinking between matches is just sensible. We certainly don’t want to keep players in their rooms because it is a long tour. You have to get out and experience what the country you’re touring has to offer.
“It’s about picking the right time to have a couple of drinks, but knowing to stay away from it if you’re preparing for a match.”
England look set to lose the first Ashes Test of the series after wilting to a 195 total in their second innings.
Australia then hit back, cutting into their 170-run chase.
The Aussies now just need 56 runs on Monday to win the first Test and have all 10 wickets in hand.
More to follow…