Scottish Fire Brigades Union (FBU) secretary John Duffy was defeated in a ballot yesterday by his rival Stephen Thomson, who will now take over as the organisation's new regional secretary.
Mr Duffy had previously drawn the ire of UK general secretary Matt Wrack after Scottish firefighters decided not to take part in a national strike against the UK Government's pension cuts.
The administration of pensions is devolved to Holyrood and the union's Scottish office had won concessions from the SNP Government and agreed to shelve its strike action.
It is understood Scotland's decision to avoid a strike angered the UK leader, who wanted a UK-wide stance.
He subsequently fired off a series of blistering emails to Scottish FBU executive council member Roddy Robertson
The messages, published by the Sunday Herald, contained attacks on Mr Duffy and criticisms of FBU Scotland's approach to the pensions dispute.
Mr Wrack wrote: "It is once again disappointing that you have acted on a pensions matter without even discussing it with me or with the national officer."
On Mr Duffy saying that Scottish union members could get "dragged into" an overtime ban, Mr Wrack wrote: "John seems to have forgotten that the Fire Brigades Union decided this campaign at a national conference and in two national ballots.
"Members in Scotland have not been 'dragged into' anything - they voted for industrial action."
He added: "I therefore must insist that no further comments are made to the press on the union's pension campaign without discussing it with us.
"If that means questions should be referred to Head Office - that would be preferable to the error which was made in these comments."
He also criticised the Scottish FBU leader for accepting an OBE, saying: "I have to say I find it a huge embarrassment that an official of this union took such an honour from the British establishment at a time when we are facing the worst cuts and attacks in history."
However, Mr Robertson replied: "The only one creating confusion in the membership in Scotland is you … I suggest that you take a step back as this is becoming tantamount to bullying and harassment."
He advised Mr Wrack to "get over" Mr Duffy's award.
The row appeared to have been swept under the carpet yesterday with the election of Mr Thomson, with neither party commenting on it directly.
The new secretary, a firefighter from Larbert who has worked for the fire service in Scotland for 20 years, won 80% of the vote to replace Mr Duffy.
He said: "It is a great honour to be elected to represent Scottish firefighters. I look forward to working with other union officials and would like to thank my colleagues for electing me to this position.
"We face many challenges and my priority is to defend our vital public services and those who work within it on behalf of our communities across Scotland."
Mr Wrack said: "I congratulate Stephen on his election and look forward to working with him.
"I would like to thank John Duffy for all the work he has done on behalf of the FBU and wish him well.
"The fire service is under attack in Scotland and elsewhere and our job is to protect it against cuts and job losses, which put the safety of firefighters and of the public at risk."