Liberal Party director Tony Nutt has warned of potential dangers and difficulties in seeking to ban foreign political donations.

With a parliamentary committee examining the issue after the Sam Dastyari controversy – in which the Labor senator took money from donors with links to the Chinese government to pay personal debts – Nutt said “sometimes in campaign finance reform it’s outrage in search of evidence”.

The first rule of campaign finance reform was “don’t make any new error” while the second rule was to “watch out for lots of unintended consequences”, he said.

Nutt, the 2016 Liberal campaign director, was answering questions at his post-campaign appearance at the National Press Club.

He said the US had been “a graveyard of well-intended campaign finance reform that winds up with hugely unhelpful developments”.

One issue was what constituted a “foreign donation”. As a migrant nation Australia had many dual citizens, he said. “Are citizens who have houses and businesses and activities in Australia, family in Australia but also in, for instance, some other countries, China, other parts of Asia, Europe, America … permitted as citizens to make donations?

"If they’re not going to be permitted to make donations, what’s the legal basis on which they’re going to be prohibited from making donations?”

It was one thing to talk about purely foreign citizens or purely foreign entities, but many of those talked about “are actually part of the wider Australian migrant experience. They’re citizens. They have businesses and families, homes, activities in Australia, just like there are a lot of Australians resident overseas and other countries.”

In his address Nutt strongly defended the campaign against criticism from some on his own side that it was not negative enough against Bill Shorten and Labor.

Qualitative research had confirmed that voters were sick and tired of political aggression and wanted to see a positive vision and plan, he said.

“There were, of course, important negative (attack and contrast) elements to our campaign, but to skew too far towards the negative would have been to devalue both this positive message and the contrast against a desperate Shorten-Labor forced to go negative through a lack of a positive plan,” he said.

If the Coalition had gone more negative it would only have boosted the vote for minor parties and independents.

He said the Coalition’s campaign “was not undermined by being positive, but was instead ‘held up’ against strong negative attacks from Labor, unions, Greens by positive appeals”.

Like Malcolm Turnbull and other Liberals, Nutt lambasted Labor’s “Mediscare” campaign. He said the claim the government would privatise Medicare was not a “garden variety lie” but a “cold-blooded lie”. “The really outrageous aspect of the Mediscare was that it was coldly, ruthlessly, and callously targeted at vulnerable Australians.”

On the difference between the Medicare campaign and the various scare campaigns by the Coalition in the past, Nutt argued it was based on a “lie” – which he distinguished from “contestable” claims.