The case at the High Court in Edinburgh against isles MP Alistair Carmichael should be dismissed, his legal representative has argued.
Roddy Dunlop QC has told judges at a televised election court that the petition was “bound to fail”.
His comments have come at the start of a legal debate chaired by Lady Paton and Lord Matthews.
The case has been brought by four of Mr Carmichael’s Orkney constituents, who are claiming the former Scottish Secretary breached the Representation of the People Act over his involvement in a story published in a national newspaper on 3rd April.
Mr Dunlop highlighted Section 106 of the Act, which states: “A person who, before or during an election, makes or publishes any false statement of fact in relation to the candidate’s personal character or conduct shall be guilty of an illegal practice, unless he can show that he had reasonable grounds for believing, and did believe, that statement to be true.”
Launching an attack against a candidate’s political position did not, he said, equate to an attack on character.
“Many people might say ‘what’s wrong with expecting honesty of our politicians?’
“The answer is that for 120 years it has been thought appropriate by parliament to distinguish between the public, or political, on the one hand, and the private on the other.
“In the last 120 years the approach advocated by the petitioners have never been suggested let alone upheld, and for good reason.”
Citing a previous case, he said: “If the cut and thrust of politics is to continue to have vigour one can not emasculate that process by creating a situation where every syllable is guarded.
“The statutory provisions were introduced for clear and good reason to prevent the traducing of private character for political gain. They were not introduced to allow disappointed electors to pour over every utterance of an opponent in an attempt to unseat him.”
Earlier in the debate Mr Dunlop called on the court to adopt a “strict, narrow view” of the Act of 1983, adding that any attack should relate to a candidate in an election.
He added it would have been an easy process for the Act to have made clear if any false statement could relate to non-candidates, but it did not do so.
The case follows the publication of a Daily Telegraph story, headlined “Nicola Sturgeon secretly backs David Cameron”.
Cabinet Secretary Sir Jeremy Heywood ordered an inquiry into the leak, and Mr Carmichael was also subject to questions by Channel 4 news.
The investigation later concluded a former special adviser to Mr Carmichael, who at the time was Scottish Secretary under the previous coalition government, had his permission to leak the story.
Mr Carmichael’s involvement in the leak only came to light after the general election had taken place, by which time he had been returned as MP for the isles – on a much-reduced majority.
• The hearing continues this afternoon. Watch it live here.