Scottish Greens co-convener Patrick Harvie has said Donald Trump's presidency could put civilised society "in peril" and urged Europeans to help Americans on the "front line" to repay their debt from the Second World War.

He said President Trump is a "bullying bigot" with "no respect for democracy" who is the "natural inheritor of fascism", and the so-called special relationship needs to be maintained with Americans threatened by the Trump residency rather than with the US government.

Agenda: Blunder and fiasco could be mark of a “Tirade Trump” presidency

Mr Harvie told an audience at the David Hume Institute in Edinburgh: "In all respects that matter, Donald Trump is the natural inheritor of fascism and so the world has to come to terms with how we deal with the reality of the threat that he poses.

"In the middle of the last century people from the US stood with Europe, fought alongside people in Europe against the fascist threat.

"And now, as the inheritors of fascism gain power in the US, we must repay that debt and act as allies with those who stand on the front lines within their own continent."

He used his address, part of a series of speeches from the leaders of Scotland's political parties hosted by the institute, as a rallying call to progressive forces worldwide in response to the resurgence of the far-right.

He said: "What we see now in Brexit, Trump and other far-right movements could be the beginnings of yet another crisis in which the basic functions of our democratic society are in peril. Or, it could be taken as an opportunity for progressive forces around the world to reset the agenda and establish a positive and empowering vision of the future."

Mr Harvie warned his party will not support the Scottish Government's draft budget unless it makes "further moves" towards progressive taxation.

Agenda: Blunder and fiasco could be mark of a “Tirade Trump” presidency

He said not making greater use of new tax powers devolved to Holyrood would be an "astonishing failure".

As a minority administration, the SNP relies on support from at least one opposition party to ensure the budget is passed when it comes before MSPs next month.

Mr Harvie said: "In the next few weeks the Scottish Parliament is going to be debating its own budget - the ability to set progressive tax, at least to go further than the status quo, to begin making moves toward a more progressive taxation.

"I think it will be an astonishing failure if we don't make any moves in that direction at all, and if the Scottish budget as it is finally presented in its final form in February has made no further moves in that direction, it certainly won't be passed by the Greens."