Auckland Transport is opening its books to the public this month, but Auckland Council won't be following suit.

The transport agency has starting publishing key details about all its contracts, rather than only contracts above $50,000 as it had previously done.

The council has agreed to reduce its reporting threshold from $100,000 to $50,00, but won't be publishing smaller contracts.

In a memo to councillors, procurement manager Jazz Singh said the council accepts "ratepayers are asking for greater transparency" about council spending.

But he said reporting smaller contracts would be "administratively challenging" and "too challenging to implement".

He said there are also some remeasurement contracts, in which the amount being paid to to the contractor won't be determined until the work has actually been done.

Auckland Transport committed to report all contracts in response to a request from Penny Bright at the board's February board meeting.

A letter from Auckland Transport to Bright, obtained by Newstalk ZB, shows the agency made the commitment just a day before former senior manager Murray None was jailed in the country's largest bribery case.

Ms Bright said council bodies are legally obligated to report all spending. She is an ongoing legal dispute over her refusal to pay rates to the council.

But in the letter, Auckland Transport chairman Lester Levy said the information has been released voluntarily, as part of the agency's commitment to act ethically and transparently.

"There is nothing in the Public Records Act which is relevant to whether Auckland Transport should or must make [information about contracts] publicly available."

Auckland Transport releases an updated list of its contracts every three months, and the council has now agreed to start doing the same.

Christchurch City Council publishes details of NZTA awarded contracts above $50,000 on a monthly basis.