A group of people have locked themselves to a railway track in Christchurch in protest of the revised TPP agreement due to be signed this month.

Six protesters, part of the group 'Our Children's Future', are chained to a railway track on Lincoln Road in Addington in opposition to the rebranded TPP agreement, supported by a group of 30 others.

The group's main concern is that the TPP will lead to further intensification of the dairy industry and lead to further pressure on local rivers through nitrate pollution.

"We need to have a conversation about water in this country before we just assume that increased exports are a good thing because of economic growth," spokeswoman Gen de Spa says.

She said there was little to gain in terms of GDP growth from the TPP as it would only increase GDP by one per cent over 20 years.

"$4 billion they reckon from the TPPA in 20 years time. We could make $3.6 billion per year from tomorrow if we charged a royalty on bottled water but we can't do that because of our Free Trade Agreements!

"You've really got to be asking 'what are the gains?' "

Ms de Spa said they decided to block the train track "to make the strongest point possible, whilst pissing off as few people as possible".

Police have confirmed they are responding to an incident where a group of protesters had chained themselves to the railway lines on Lincoln Road in Addington. They are currently at the scene speaking to them.

KiwiRail has been advised.

The revised TPP agreement is set to be signed in Chile on March 8.