Malcolm Turnbull has ridiculed Labor leader Bill Shorten for seeking to co-operate on policy.
The Labor leader has in recent times written to the prime minister offering bipartisan support on a number of issues from national security to climate change.
Mr Turnbull described the letters as "sanctimonious" and were always followed up by political attacks by "the old Bill".
"The honourable member can write me lovely letters, he likes to write me letters and he is always so sanctimonious in his letters," Mr Turnbull told parliament on Tuesday.
"This is 'Good Bill', this is the goody two shoes and he always appeals to bipartisanship and he sends the letter around and I am sure he feels really good about it."
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Mr Shorten has argued "continued, thoughtful bipartisan co-operation" is the key to addressing major issues such as national security.
