Labour's "Axe the Tax" bus trip protesting GST increases is costing the taxpayer about $30,000 - but Labour leader Phil Goff has defended it as the cheapest way to get around the country on an issue that affects everybody.

The Labour Party has chartered the bus for a fortnight-long nationwide trip protesting against the Government's proposal to increase GST to 15 per cent, with compensatory tax cuts that Labour claims will advantage high-income earners.

The bus features a red "skin" with Axe the Tax signage and Labour logos.

A spokesman for Mr Goff said the costs were expected to be about $30,000, including for the bus charter, the signage and other material such as signs and balloons.

It was funded out of Mr Goff's parliamentary leader's office fund.

He said it was a fraction of the $200,000 bill to the taxpayer for brochures Prime Minister John Key sent out to households last month to defend his party's new national standards policy for schools.

Mr Goff defended the decision to make the bus trip, which follows an earlier journey by the Labour caucus to reconnect with voters.

"GST is a universal issue and I make no apologies at all about value for money. What do people expect from their MPs? They expect them to get off their bums and do their job. And getting out there by bus is hardly extravagant."

Mr Goff said GST was an issue that affected everybody in a way few other issues did. The bus was the cheapest way to get around the country and to places that were not on main transport routes.

It would cost significantly more for him to use Crown cars to travel around in and for other MPs to use individual forms of transport. The signage was attention-grabbing and ensured people knew exactly what the MPs were there to talk about.

Accommodation expenses for the Labour MPs were likely to be low as most were joining the bus only when it was in their home regions.

Under Parliament's funding rules, MPs can use public funds to communicate their policies and messages to the voters.

The National Party brochures - coloured blue and carrying the National Party logo - went to 350,000 households and were paid for out of Mr Key's parliamentary party leader's fund because they promoted party policy and were not official ministerial or government department material.

The PM issued them early last month after a concerted campaign and threats of boycotts of the standards by teacher unions and Labour and concerns from academics that the implementation was wrong.

The Green Party also uses its parliamentary funding to campaign against policies - including green rubber wristbands with "Life Cycle" and the party's logo and website engraved on them. It also issued anti-mining stickers at Waitangi Day.

Mr Goff said the tour had so far gone well, with many in small towns such as Putaruru commenting how surprised they were to see MPs. "Whatever they say about their politicians, people don't actually mind seeing them face to face."

Next week, David Cunliffe and Annette King will take over for some of the South Island leg while Mr Goff and Rick Barker visit Northland on their motorbikes. They will be joined by local MPs while there.