As many as one in five federal politicians are using their travel allowances to supplement the cost of second homes in Canberra.

Politicians are entitled to claim $273 a night when they travel to Canberra for Parliament or other business and many keep second residences in close proximity to Parliament House.

Representatives for ministers including Finance Minister Mathias Cormann, Social Services Minister Christian Porter, Indigenous Affairs Minister Nigel Scullion and Assistant Defence Minister Michael McCormack confirmed they stay in houses or apartments they own and claim the travel allowance when in Canberra, which can work out at a minimum of $1000 a week or $18,000 a year.

"This is part of the remuneration and work expenses arrangements for members of Parliament as determined by the independent Remuneration Tribunal," a spokeswoman for Senator Cormann said.