Immigration Minister Scott Morrison has denied trying to sweep extra roles into his portfolio as he sets up the Australian Border Force.

Mr Morrison is bringing together staff from the immigration and customs area sunder the single umbrella of the Australian Border Force agency.

But his streamlining project has given rise to claims he wants a slice of foreign affairs, defence, justice and agriculture.

Fairfax Media is reporting that the Immigration Minister has been looking at other minister's portfolio responsibilities, including speculation that he wants to take charge of bio-security, which is currently with Agriculture Minister Barnaby Joyce.

The Australian Financial Review says a tussle over responsibility for bio-security has been underway for months between Morrison and Joyce.

Mr Morrison denied the claims in an interview with the ABC today.

“What is happening is we are working to implement the decision to establish a single border agency. There's no question of agricultural bio-security issues being affected at all on these sort of matters,” he told reporters.

“The primary role that is occurring with the single border agency is merging the immigration and customs functions, which are completely within my own portfolio.”

“What has been discussed in the implementation of the single border agency is how we can do things seamlessly at the airports and that does not require the integration of agricultural functions into that agency. And certainly, in relation to agricultural bio-security, then of course that's the proper domain of the Department of Agriculture.”

Mr Joyce argued in question time this week that various departments such as his and that of Health Minister Peter Dutton needed to work seamlessly together, but “we are already doing that”, he said.