Maori TV was pressured into changing its bid for the exclusive free-to-air rights to the Rugby World Cup to allow rival channels to piggy-back and show the games.

The change points to possible political interference, as Maori TV made the change only after the National Government became aware of the $3 million taxpayer-funded boost the bid received from Te Puni Kokiri.

Maori TV spokeswoman Sonya Haggie confirmed the station had originally asked the International Rugby Board for exclusive rights.

She said it had gone back to the IRB last week and asked if it could modify its bid to allow it to sub-license the rights.

Ms Haggie refused to say why Maori TV had asked for the change, which happened at about the same time as the Herald became aware of the controversial funding boost from Te Puni Kokiri.

The rights include the live coverage of 16 games, including all the All Blacks' matches and the finals.

Prime Minister John Key has said he expected 100 per cent of New Zealand to be able to see these games live, while Maori TV gets to only 90 per cent of those without Sky or Freeview.

Sub-licensing would allow TVNZ or TV3 - whose bids were far lower than Maori TV's - to show the games and largely meet Mr Key's expectation.

Ms Haggie said Maori TV would on-sell the rights to the games for an appropriate commercial price.

But such an arrangement would limit the audience numbers for Maori TV's coverage, meaning fewer would be exposed to the Maori language and culture that Maori Affairs Minister Pita Sharples said was the reason for Te Puni Kokiri's funding boost.

Broadcasting sources told the Herald a sub-licence to broadcast into Maori TV's black spots would be technically impossible and commercially unworkable.

The sources said TVNZ and TV3 would most likely want to use their own people to commentate on the matches. It was unlikely either broadcaster would agree to screening Maori TV's coverage, as this would damage their brand.

The Herald has learned Te Puni Kokiri's deal will give the broadcaster $1 million a year for the next three years.

Finance Minister Bill English raised concerns after learning of the Te Puni Kokiri funding in September in a letter from Associate Maori Affairs Minister Georgina te Heuheu - but the bid had already gone in days before on September 4.

A spokesman for Mr English said he was overseas when Mrs te Heuheu's letter arrived and he did not see it until the week of September 7.

"On receiving the letter, the Finance Minister and his office raised concerns about the process and the proposed TPK funding with both TPK and Minister Sharples."

Mrs te Heuheu indicated in the letter that the same information had also been forwarded to Mr Key - although that turns out not to be the case. The letter to Mr Key said Maori TV was bidding but did not mention the financial support by Te Puni Kokiri.

Mr Key said if Maori Television won the bid, Dr Sharples and Te Puni Kokiri would need to prove to the New Zealand public that it was a good use of taxpayers' money.