Nicola Sturgeon has accused Andy Burnham of "generating a spat" with her over Scotland's newly-imposed Greater Manchester travel ban, as the political fallout from the decision continues.
"If he wants a grown-up conversation, he only has to pick up the phone," she told Sky News on Monday.
"I've always got on well with him, but if this is more about generating a spat with me as part of some positioning in some kind of Labour leadership contest in the future, then I'm not interested."
Mr Burnham said accusations of political posturing were unfounded and that he too is only acting in the interests of his residents as part of a devolved administration.
"Shouldn't she have picked up the phone?" he said.
"It's very discourteous, not to me, but to the people of Greater Manchester for this to be done in this way."
He said that he has received emails from residents who are "thousands of pounds out of pocket" as a result of the decision.
People have had to cancel holidays in the Highlands and businesses with links to Scotland have been impacted, he added, saying Ms Sturgeon's actions are an "insult" to them.
"I'll send the first minister all the emails that I've had," he said.
"The SNP are always the first to say 'the Westminster government has done something to us and not told us about it first'.
"Well we're a devolved administration too here in Greater Manchester - we have a devolution from Westminster - so you would expect there to be an understanding of that from the Scottish government."
Ms Sturgeon has said the decision was made over concerns about case numbers of the Delta (Indian) variant in Bolton, Salford, Manchester and Lancashire.
But Mr Burnham claimed that Bolton's case rate is "significantly lower" than parts of Scotland, such as Dundee, making the ban "unfair".
Bolton's seven-day average COVID case rate is 269.2 per 100,000 people, while Dundee's is 318.1.
However other areas of Greater Manchester, such as Manchester itself (339.7) and Salford (340), have higher infection rates than parts of Scotland, such as Glasgow (159.1) and East Lothian (170).
Announcing the ban, which came into effect on Saturday, Ms Sturgeon said: "Anyone travelling elsewhere in the Greater Manchester or Lancashire area, I'd ask to think carefully about whether your journey is really necessary, because we do see cases rising across that region."
But opposition politicians in Scotland have said the decision "doesn't make sense".
Lib Dem MSP Alex Cole-Hamilton applauded Mr Burnham for standing up to the first minister, saying that some parts of Scotland have "transmission rates equal to that of Manchester".
The ban stops anyone from Bolton, Manchester, Salford or Lancashire travelling to Scotland and vice versa.