The development agency said the package of measures agreed at a major summit in Brussels on Friday were "woefully inadequate".
Christian Aid that European leaders had seriously damaged their credibility with the new US administration of Barack Obama.
Alison Doig, Christian Aid's Senior Adviser on climate change, says: "We had hoped that the EU would set a leading example to other rich countries – one which would inspire them to agree similarly ambitious targets.
"We are deeply disappointed by the agreement which looks set to emerge from Brussels.
"By failing to adopt a more realistic plan to help keep global temperatures within safe levels, EU leaders have seriously damaged the quest for an effective and equitable solution to the climate crisis."
Christian Aid pointed to calculations of its partner EcoEquity, which has found that emissions cuts of only 20 per cent – equivalent to the latest EU agreement – will not be enough to prevent a "devastating" global temperature rise of more than 3C.
"This would be catastrophic for people around the world and especially for those in developing countries, who are the most vulnerable of all," said Ms Doig.
"Christian Aid urges the European Parliament to show much greater support for strong European emissions cuts when it votes next week on the 'effort sharing' part of the EU package, and to reject today's deal."
Christian Aid said it was also concerned that the agreed cuts would be achieved largely by 'buying in' cuts from developing countries. The aid agency said that it was essential that imported cuts are in addition to any domestic cuts.
Ms Doig says: "Another major concern is the EU plan to give almost full exemptions from buying emissions permits under the European Emissions Trading Scheme to the very industries which pollute the most. This perverse decision, if allowed to stand, will dramatically reduce the scheme's power to help safeguard the world's climate."
The EU agreement was reached just one day ahead of the conclusion of another major climate change summit in Poznan, Poland, focusing on adaptation funds.
A delegation representing the World Council of Churches told the United Nations Climate Change Conference on Friday that an effective and equitable global climate policy regime must be built on the principles of justice, equity and solidarity.
The two-week summit concluded on Saturday without a deal on funds to help poor nations adapt to climate change.
Speaking on behalf of the WCC delegation, the Primate of the Church of Sweden, Archbishop Anders Wejryd urged government leaders not to miss the small window of opportunity that still remains to prevent the most detrimental effects of climate change on nature, society, the economy and development.
Drawing from the Interfaith Climate Summit in Uppsala, Sweden at the end of November, the statement also underscored the role of faith communities in promoting hope and trust in the "feasibility of climate proof, sustainable societies and lifestyles that will enhance life with dignity".
"Meeting this year in PoznaÅ", we feel the urgency as we think we have only a small 'window of opportunity' of less than 10 years in which to stabilise atmospheric concentrations of greenhouse gases, limit atmospheric temperature rise to 2C and at the same time prevent the most detrimental impacts on nature, societies, economies and development opportunities," said Wejryd.
"But as a Christian fellowship of churches we also do this with faith, because we know the needed changes are possible and believe in the promise of "…a new heaven and a new earth…" (Book of Revelation, 21:1), where justice, equity, solidarity, peace and love will prevail.
"As churches, faith is the reason for us to act. We share this inspiration with other faith traditions.
"Thus the feasibility of adequately addressing climate change depends very much on the political will and consequent decisions this COP will make."