Gordon Brown was warned by the Commons Speaker Michael Martin to use "temperate language" after he accused David Cameron of "misleading" people.
The exchanges came after the Tory leader claimed the Gould report into the Scottish elections said ministers had put party interest before voters.
The PM said: "You're misleading people about the conclusions of that report."
That sparked protests from Tory MPs and Mr Martin issued his warning after he consulted with the Commons clerks.
But the Speaker rejected calls for tougher action, saying he was "satisfied the prime minister said nothing unparliamentary".
Mr Cameron asked how Mr Brown "had the gall" to accuse him of misleading people over the report.
The accusation from Mr Brown led to angry exchanges between Tory MPs and the Speaker after prime minister's questions, with a number bringing up the matter during points of order.
Tory MP Andrew Mackay asked the Speaker if Mr Brown should apologise to Mr Cameron and withdraw his remarks.
He said it was "both out of order and unparliamentary language for one member to accuse another member of misleading the House, as clearly the prime minister did to the leader of the opposition".
Tory chief whip Patrick McLoughlin asked: "Can I therefore take it that it's quite in order for a member of Parliament to accuse another member of Parliament of misleading the House?
"In which case we will bear that in mind when we come to challenge the government."
Mr Martin said he understood the chief whip's "anxiety".
"All I can say is read the record of Hansard tomorrow. I ask you to take my word for it," he said.
"Honourable members have got to understand that I'm in the chair and it's a rolling situation.
"I have consulted the record and I'm satisfied that the prime minister has said nothing unparliamentary."
Mr Martin told Mr McLoughlin he was always entitled to come and see him about the matter.
Labour left-winger Dennis Skinner, who was once rebuked for calling a fellow MP a "squirt", weighed in to add that it would be a different matter if Mr Brown had said an MP had been "deliberately misleading the House".
Both the Scotland Office and the Scottish Executive were frequently focused on partisan political interests in carrying out their responsibilities, overlooking voter interests
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"I have been around a long time - I've tested the market and it's called experience," he joked.
Mr Martin was forced to "call for temperate language" after Mr Brown claimed Mr Cameron was "misleading" people by suggesting that a critical report into the Scottish elections fiasco only blamed one party.
Mr Brown said all political parties should share the responsibility because they had agreed the system adopted for the 3 May poll in which 140,000 ballots were rejected.
But this prompted Mr Cameron to say: "I don't know how you have the gall to accuse me of misleading anybody," adding that the prime minister had pledged, on taking office, "to be more open and honest".
Decisions on whether MPs have used "unparliamentary language" are taken by the Commons Speaker - the person who chairs proceedings in the Commons chamber.
It is expected that the proceedings of Parliament be conducted in a courteous and good tempered manner although criticism and accusations are permitted.
MPs are not, however, allowed to accuse another member of Parliament of lying, suggest another MP has false motives, misrepresent another MP's language or use abusive or insulting language.
If an MP uses unparliamentary language during debates the Speaker will ask the member concerned to withdraw what has been said.