The Pope has denounced the love of money as "the devil's excrement" in an address on his visit to Bolivia this week. He has also called for an end to what he says is "genocide" against Christians in the Middle East.

Speaking to leaders and members of the country's many popular movements in Santa Cruz de la Sierra in eastern Bolivia, Pope Francis returned to his ongoing passion, defence of the environment.

He warned of "irreversible" damage to the ecosystem in the name of profit.

Using a term that he said was originally coined by St Basil the Great, he described the "stench" of the devil's excrement. "The unbridled ambition of money dominates. This is the 'the devil's excrement'. And the service of the common good fades into the background."

The term "the devil's excrement" was also popularised by Venezuelan Juan Alfonso who used it to condemn the easy wealth produced by oil.

In his address, available in Italian and Spanish on the Vatican website, the Pope warned against greed for money and for making an "idol" of capital and allowing it to direct the actions of human beings.

The Pope was speaking towards the end of his week-long trip to Ecuador, Bolivia and Paraguay, three of the smallest and poorest nations in South America.

He said change was possible, but only if there was first a change of heart.

For this to happen, the economy had to serve humans and not the other way around. "Human beings and nature must not be at the service of money. We say 'no' to an economy of exclusion and inequity where money dominates instead of serving. This economy kills. This economy is exclusionary. This plan destroys Mother Earth."

The Pope went on to criticise the many faces of a "new colonialism" which he said used the power of the "idol" of money to control "free trade" and impose "austerity".

He said: "Colonialism, old and new, which reduces the poor to mere suppliers of raw materials and cheap labour, generates violence, poverty, forced migration and all the evils that we can see. This led to inequity and violence that no police, military or intelligence services can stop."

Pope Francis admitted that the Church had itself committed many serious sins against the native peoples of America in the name of God. "Like St John Paul II, I ask that the Church should kneel before God and implore forgiveness for the past and present sins of her children." But church people had also been a force for good, he added.

The Christian faith is revolutionary and challenges the tyranny of money. "Today we see with horror as in the Middle East and other parts of the world, many of other brothers are persecuted, tortured and murdered because of their faith in Jesus." This must be denounced, he said. "There is a kind – I force the term – of ongoing genocide that has to stop."

Earlier in the week, addressing hundreds of thousands of pilgrims at Los Samanes Park in Guayaquil, Ecuador, the Pope referred to the coming Ordinary Synod on the Family in Rome this autumn, and said the family was in need of a miracle.

There were many difficult and important challenges that the family today faces, the Pope said. Even things that seem "unclean" and which scandalise or frighten, can be transformed by a miracle.

Issues likely to be addressed at the synod include the remarriage of divorcees and the place of homosexuals in the Church.