Fine Gael was accused of “congratulating itself”on tackling climate change at the party’s Ardfheis on Saturday, while environmentalists in Dublin and cities across the world were rallying under the Extinction Revolution banner.

At a rally outside the National History Museum and Leinster House an estimated crowd of 500 people – many of them families with small children – heard calls for people to “take back our future and stand up for the living planet”.

Writer and activist Carolyn Moore told the crowd Fine Gael were “at their conference saying climate change is a priority for them. Well, you could have fooled me.”

Ms Moore said the Extinction Rebellion rallies were taking place simultaneously in Dublin, Cork, Galway and Belfast as well as across the world in London, England, Copenhagen in Denmark, Berlin Germany, Stockholm Sweden, New York in the USA and Madrid in Spain.

Ms Moore Introduced a range of speakers including members of the Labour, Green, People Before Profit, Sinn Féin and Solidarity parties as well as non-governmental agencies while urging the crowd to repeat the refrain; “When our planet is under attack, we stand up and we fight back”.

Protesting against ecological collapse. Photograph: Nick Bradshaw

A number of speakers referred to a recent World Wildlife Fund report which claimed that humanity was responsible for wiping out 60 per cent of mammals, birds, fish and reptiles since 1970.

The report has lead to the world’s experts warning that the annihilation of wildlife is now an emergency that threatens civilisation. “We are in the midst of an ecological crisis over pillaging the earth’s resources” she said.

Fellow environmentalist 11-year-old Flossie Donnelly, who was one of the first to report plastic contamination of bathing waters and the shore in Dún Laoghaire in recent weeks, introduced herself to sustained applause with the words “my name is Flossie and I clean the beach”. She said a seal had been found dead on the beach and plastic and crisp bags “were found in its tummy. Now that’s crazy.”

Dara McAnulty (14) from Fermanagh called for a boycott of palm oil, single-use plastics and and end to the use of fossil fuels. He said the planet was being handed over to a new generation in a worse condition than that in which it had been inherited.

Pádraic Fogarty of the Irish Wildlife trust said it was “extremely appropriate to be angry” about climate change and species extinction as the planet was being “whittled away for greed and profit”. He was followed by Bríd Smith TD who said the UN’s Intergovernmental Panel on Climate Change had determined there may only be 12 years remaining where meaningful action can be taken to avert dangerous climate breakdown. She said the report should “send shivers down the spine” of the Government which she said “fiddled while the planet burns”.

Green Party Senator Grace O’Sullivan – dressed in a wet suit to highlight the threat to marine life – said It was necessary to transit to renewable energy which would be good for the economy. Michael Coughlan of Climate Case Ireland said the organisation was taking the Irish Government to court for failing to take action to avert dangerous climate change. The case was due in January.