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The Green MP says the 800km trip on the taxpayer dollar was essential, but a taxpayer group queries whether it was fiscally and environmentally responsible.
On Friday, Parliament's only deaf MP flew from Christchurch to Wellington, then drove to Masterton, to participate in ArrowFM's Wheels on Fire programme for people with disabilities.
ArrowFM is one of 12 Community Access Radio stations in New Zealand, and the only community station in Wairarapa. Its audience is not known, but its Facebook page has 132 "likes".
Last night Ms Mathers said the journey was a necessary expense because it was "almost impossible for me to do live interviews over the phone".
She needed to be face-to-face with the interviewer in order to lip read, she said, especially for a one-hour show.
"As the only disabled Member of Parliament it is really important I represent disabled New Zealanders, which make up one in five New Zealanders," she said.
"MPs do have to fly a fair bit to get out to our communities. All Green MPs offset our air travel and try to minimise it as much as possible.
"I consider all requests to meet very carefully, including this one, and I felt it was really important to take this opportunity to speak to disabled New Zealanders living in rural communities."
She did not know the cost of the trip, she said, but it would be declared as part of her expenses, and was planned in line with other work she had to undertake in Wellington.
Standard Air NZ flexible fares between Christchurch and Wellington are $199 each way. A small rental car from one of the suppliers used by the Parliamentary Service is $148 - so the trip is likely to have cost the taxpayer a little under $550.
The Taxpayers Union questioned whether it was value for money.
"It's amazing that she has so little to do with her time to actually travel to a community radio that probably has as many listeners as you can count on your hand," director Jordan Williams said.
"The only silver lining is that the time spent travelling to go on the station in the middle of nowhere is less time spent dreaming up new ways to spend tax payers money."
- Patrice Dougan