Labour has again changed its position on the foreshore and seabed, withdrawing its support for the bill repealing the current law while it is part-way through the select committee process.

The flip-flop does not jeopardise the ability of the bill to be passed.

National and the Maori Party still have the numbers to pass the Marine and Coastal Area (Takutai Moana) Bill - with 63 votes out of 122.

But the cushion is now much slimmer.

They can afford to have only one more MP switch sides before they lose the numbers to pass the bill.

Labour's decision ends the sense of broad cross-party agreement that accompanied the bill's first reading in September.

Previously only Act and the Greens opposed the bill; now only National, Maori and United Future's one MP support it.

Labour's decision comes in the third week of select committee submissions on the bill and, with the amount of opposition to the bill by Maori and others, it may figure it does not have a lot to lose by another switch.

Labour leader Phil Goff said he was trying to get the numbers from other parties for an alternative to the current bill.

The party wants to drop any political involvement in customary title and hand it all back to the courts, a position favoured by Act and by National in Opposition.

The current bill restores the right of iwi to claim customary title in the courts, or to negotiate directly with a minister privately and get title by simple regulation.

In either case there would be a qualifying test.

* 2004: Labour Govt passes Foreshore and Seabed Act asserting Crown ownership, preventing Maori from claiming customary title in court, but setting up alternative regime of rights.

* 2009 April: Labour in Opposition renounces F&S Act saying it would support law restoring right to go to court.

* 2009 Nov: Leader Phil Goff says there is nothing wrong with the way F&S Act is working and repeal would be cynical.

* 2010 Sept: Labour supports new bill designed to repeal F&S Act.

* 2010 Dec: Labour withdraws its support for the bill.