The committee Malcolm Turnbull insists is the best way to reform Australia's political donations system has not been formed, has not been asked to examine the issue and routinely had its past recommendations ignored.

A day after Labor senator Sam Dastyari fell on his sword after revelations he asked Chinese donors to pick up bills and that he contradicted Labor's South China Sea policy, Mr Turnbull and his ministers have dodged questions about donations reform, insisting it is a matter for a little-known committee of Parliament.

Speaking in Laos, Mr Turnbull said he had long argued for donations to "ideally" be restricted to people on the electoral roll - a move which would ban unions, corporations and foreigners from tipping in money to politicians and political parties.

But the Prime Minister added that donations reform was "a very complex issue and it is something the JSCEM [Joint Standing Committee on Electoral Matters] should look at carefully", a line he has repeated all week.