Bill Shorten has doubled down on plans to end cash refunds for excess franking credits, saying the May 18 election was a fundamental choice between funding such "gifts'' and funding better health care.

As Prime Minister Scott Morrison used Labor's proposed higher tax burden to warn a change of government could cause a recession,  Mr Shorten highlighted the franking credit cash refunds as an example of  "the intergenerational bias in our tax system'' that Labor would "end".