France has been told by Nick Clegg to end "simply unacceptable" attacks on the UK economy, amid mounting cross-Channel tensions over the eurozone crisis.
French prime minister Francois Fillon telephoned the Deputy Prime Minister to insist he had not intended to call into question the UK's credit rating.
Mr Fillon and the head of the French central bank had suggested Britain should be a candidate for a downgrade amid fears in Paris that France might lose its coveted AAA rating.
His finance minister Francois Baroin further inflamed the situation on Friday by calling the UK's situation "very worrying" and suggesting France was better off.
Downing Street resisted any direct retaliation but Mr Clegg launched a furious retort in his conversation with Mr Fillon.
A spokesman said: "PM Fillon called from Rio de Janeiro to clarify his recent comments about the UK's credit rating.
"Fillon made clear it had not been his intention to call into question the UK's rating but to highlight that ratings agencies appeared more focused on economic governance than deficit levels.
"The Deputy Prime Minister accepted his explanation but made the point that recent remarks from members of the French government about the UK economy were simply unacceptable and that steps should be taken to calm the rhetoric.
"PM Fillon agreed and they both undertook to speak again shortly to discuss economic co-operation."
The row broke out following Prime Minister David Cameron's decision to veto a pan-EU treaty to deal with the crisis in the single currency.