Adam Weymouth and Matilda Gifford from Plane Stupid Scotland, which is opposed to airport expansion, scaled the front of Holyrood this morning.

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After taking position in an area above a canopy at the front of the building, they unfurled a banner on behalf of the organisation.

The pair, both 23, came down voluntarily at around 2pm, after more than five hours on the roof – and a number of interviews with TV and radio stations.

They were arrested by Lothian and Borders Police and taken to St Leonards police station.

Plane Stupid said the protest was over the Scottish Government's consultation process for the sanctioning of major developments, including airport expansions.

The group said they felt the process was "incompatible" with the Scottish Government's plans to mitigate climate change.

The banner read: "Planestopping. Choose a future. Say no to airport expansion."

Mr Weymouth said: "We are facing a runaway climate threat but the Scottish Government's reaction is to triple air traffic and expand Glasgow and Edinburgh airports whilst conveniently excluding aviation from the Scottish Climate Bill.

"The climate scientists have made it clear – we have to stop airport expansion. That's why we've taken it to the top."

A Lothian and Borders Police spokesman said: "A man and a woman have been arrested following a protest that took place today at the Scottish Parliament."

Plane Stupid said it was opposed to the Scottish Government's National Planning Framework proposals.

Under this, ministers would have the final say on major national developments.

Improvements to Glasgow and Edinburgh airports are among the infrastructure schemes identified in the framework.

Plane Stupid said it was against the plans as public or parliamentary approval would be "bypassed".

Today's protest was timed to coincide with the end of the consultation on the NPF proposals, which finishes tomorrow.

Miss Gifford said: "The environmental and democratic credibility of this framework is zero. Without reducing aviation and emissions there will be no future to plan for."

The Scottish Government has set the target of an 80% reduction in Scottish emissions by 2050.

Just a few weeks ago Plane Stupid activists in London climbed on to the roof of the Palace of Westminster to protest at plans for a third runway at Heathrow.

The Tories criticised the response to today's protest as a waste of taxpayers' money.

Tory MSP Liz Smith said: "If people are foolish enough to climb on to the roof of the Parliament to stage a protest then that is their business.

"But I am sure that the taxpayers of Scotland will be astonished to learn that the actions of these two people have tied up thousands of pounds of vital resources."

She said an ambulance with two paramedics, a fire engine and four firefighters, and "a small posse" of police were on hand for hours in case of an accident.

"The rest of us have to have an accident before the emergency services rush to our aid," she said.

"But it seems that those who decide to put themselves in peril – however remote the risk – get preferential treatment and their own special rapid-response team."