John Key will attend the climate change leaders conference at Copenhagen.

Mr Key made the announcement today following wide-spread criticism from the Green Party and environmental lobby groups.

"I have reassessed our position and taken advice from our negotiating team. I have decided that on balance it makes sense for me to be there for the leaders' meeting," Mr Key said.

He said while it is unlikely a binding agreement will be achieved at the summit, because other leaders will be present, he has decided to attend.

"We go to Copenhagen with a settled emissions trading scheme on the books, a credible mid-term emissions target, and talented and knowledgeable representation at the negotiations in the form of ministers Tim Groser and Nick Smith.

"Important decisions may be made in Copenhagen and it is important that I am there alongside other leaders so New Zealand has input at the highest level," Mr Key said.

The Herald reported this morning that Mr Key had booked airline tickets to Copenhagen saying it was a "precautionary step".

He has previously said that there was only a 5 per cent chance he would make it.

Mr Key has come under pressure to attend after a flurry of diplomatic activity in the past three weeks which has given greater confidence that a new deal could be sealed there.

President Nicolas Sarkozy of France, conference chairman and Danish PM Lars Rasmussen, and UN Secretary-General Ban Ki-moon made personal pleas for leaders to go when they spoke at the Commonwealth summit in Trinidad and Tobago.

More than 90 leaders are now going to the two-week talks to negotiate a replacement for the Kyoto Protocol.

They start on Monday.

Mr Key said yesterday that he had advice from the Ministry of Foreign Affairs and Trade that the situation had "slightly changed".

Australian Prime Minister Kevin Rudd is understood to have lobbied him to go. But Mr Rudd's own leadership position in the climate change conference has been dealt a blow with the ousting of Liberal leader Malcolm Turnbull over his pledge to support Mr Rudd's emissions trading scheme.

National, with the Maori Party's support, passed amendments to Labour's ETS just a few weeks ago.

Mr Key said the result in Australia was "not entirely unexpected".

"But what it does show is how contentious climate change legislation is and how it is not just New Zealand but every country struggling to deliver on the political goodwill when it comes to climate change."