Canada will provide $2.65 billion over five years to help developing countries deal with climate change, Prime Minister Justin Trudeau announced Friday at the Commonwealth summit in Malta.

The announcement comes ahead of the United Nations鈥 climate change summit in Paris, which begins Monday.

"Canada is back and ready to play its part in combating climate change and this includes helping the poorest and most vulnerable countries in the world adapt," Trudeau said in a statement.

The $2.65-billion announcement is part of Canada鈥檚 pledge to contribute to an international climate fund that aims to raise US$100 billion every year by 2020.

Speaking to CTV鈥檚 Power Play, Liberal MP Peter Schiefke described the investment as a pre-emptive measure before climate change gets worse in developing nations, which will inevitably turn to the West for aid.

鈥淭he reality is that climate change is going to affect those most vulnerable, particularly those living in developing nations, far greater than it is going to affect us here in Canada, the United States and Europe,鈥 Schiefke said.

鈥淲e would rather invest now 鈥 than to basically be on the hook for tens of billions of dollars 20, 30 years down the road when these countries are calling on Western countries.鈥

Conservative environment critic Ed Fast described the investment as 鈥渋rresponsible鈥 and said his party is 鈥渁sking a lot of questions鈥 about the funds.

鈥淨uestions such as who鈥檚 paying for this $2.65 billion that is going to be spent outside of Canada? I think we all know the answer to that. It鈥檚 taxpayers,鈥 Fast said.

Instead, he insisted that 鈥渢hose funds could be better invested here in Canada.鈥

Schiefke shot back by targeting Stephen Harper鈥檚 environmental legacy, saying that 鈥渘ot taking any action on climate change for 10 years was irresponsible.鈥

But NDP environment critic Nathan Cullen said it鈥檚 been more than 10 years since Canada鈥檚 environmental policy has been off track.

鈥淚t鈥檚 been since these talks began 21 years ago. Canada first showed up (and) eventually signed on to some ambitious targets under the Chretien Liberal government (and) failed dramatically to reach those,鈥 Cullen said.

Reiterating comments made earlier Friday by NDP Leader Tom Mulcair, Cullen called on Trudeau to outline a detailed plan for climate change ahead of the Paris talks.

鈥淐anada鈥檚 influence will be somewhat muted if Canada is unable to tell the world what our commitment is going to be,鈥 he said. 鈥淲hen will Canada have a goal to show the world?鈥

The $2.65-billion announcement was quickly welcomed by World Vision Canada, which described the investment as 鈥渁 good first step.鈥

鈥淲e are eager to work with the government to see that Canada focusses its efforts on supporting people individuals and communities, especially children, who are the most vulnerable to the hardships of climate change,鈥 said Jennifer Slawich, senior policy advisor for World Vision Canada, in a statement.

Climate change is at the top of the agenda as Trudeau joins leaders of Commonwealth countries in Malta for a three-day summit.

Foreign Minister Stephane Dion has called the meeting a 鈥渢raining camp鈥 for the United Nations鈥 climate change conference, which begins next week in Paris. But the heads of 53 nations formerly under British rule will also be discussing terrorism, national security and the ongoing refugee crisis, CTV鈥檚 Ottawa Bureau Chief Robert Fife reported Friday.

Fife said that Trudeau was expressly asked to attend the biennial meeting of the Commonwealth leaders by U.S. President Barack Obama and German Chancellor Angela Merkel, who wanted him to stress the importance of a climate change agreement at the end of talks in Paris.

Dion has said that he expects the negotiations at the COP21 conference in Paris to be 鈥渋ntense,鈥 but he believes they will end with a 鈥渞obust agreement鈥 on how to tackle the effects of climate change around the world.

Queen Elizabeth II opened the summit in Valletta Friday by praising the accomplishments of the Commonwealth nations.

"Prince Philip and I first came to live here in Malta in 1949, the year the Commonwealth was founded," she said. "I have been privileged to witness this transformation and to consider its purpose."

French President Francois Hollande is also expected to address the Commonwealth leaders on Friday. He鈥檚 the first French head of state to make a speech at the Commonwealth summit.

With files from The Canadian Press