A majority of Scottish MSPs now support the introduction of a Robin Hood Tax to tackle poverty at home and abroad, and climate change.
So far, a total of 68 MSPs have shown their support for the move ahead of a meeting on the issue with the Finance Secretary John Swinney in Edinburgh on Wednesday.
Judith Robertson, Head of Oxfam Scotland, will hold talks with Mr Swinney alongside the Robin Hood Tax Campaign, the STUC, NUS Scotland and the Poverty Alliance.
Together they will call on Mr Swinney to champion the measure at home and abroad.
50 MSPs have signed Oxfam's Scotland's online petition with a further 18 having signed a motion supporting the tax at the Scottish Parliament.
It means if a vote on the issue was held at Holyrood, the Robin Hood Tax would win majority support - sending a clear message to the UK Government at Westminster.
Judith Robertson, the Head of Oxfam Scotland, said: "It is great news that a majority of Scottish MSPs have now come out in support of the Robin Hood Tax.
"This reflects our poll showing that 62% of the Scottish public also want this tax.
"We now need the Scottish Parliament to send a clear message to the UK Government that they should be pushing for banks to pay their fair share."
In February a wider coalition of civic organisations in Scotland signed a joint letter to the First Minister Alex Salmond calling for him to support the tax - including Unite, Christian Aid, SCIAF, Tearfund, Stop Climate Chaos Scotland, the Public and Commercial Services Union, Friends of the Earth Scotland, and the World Development Movement Scotland.
In April, Mr Salmond signalled his support for a Robin Hood tax, branding the measure "such an attractive idea" and vowing to "speak up in favour of the concept".
A global Robin Hood Tax at an average rate of just 0.05% imposed on financial transactions such as derivatives, bonds and foreign currency could raise £250 billion a year.
This equates to just 50p on every £1,000 traded - compared to VAT at £200 per £1000 - and would not apply to retail banking.
In the UK alone, extending the existing tax on share transactions to bonds, currencies and derivatives could raise at least an extra £20bn to tackle poverty and fight climate change.
The Robin Hood Tax has won influential supporters at home and abroad. In this country, it is backed by Cardinal Keith O'Brien and Nobel-prize winning economist Joseph Stiglitz, who sits on the Scottish Government's Council of Economic Advisers.
Overseas, it is supported by the billionaire businessman Bill Gates, the Vatican, the investor Warren Buffett and over a thousand economists. This week German Chancellor Angela Merkel said she will push for as many countries as possible to be part of a European FTT - yet the UK Government remain steadfast in their opposition to this proposal.
Last month the European Parliament voted in favour of an FTT by 487 to 152.
Judith Robertson added: "Scotland's MSPs are joining an ever growing list of influential supporters of the Robin Hood Tax - they now need to actively champion for this tax.
"By doing so, they can help show that David Cameron and George Osborne are isolated not just within Europe, but within the United Kingdom."
Sign the "Scotland Backs the Robin Hood Tax" petition
The 50 MSPs who signed the petition are: Iain Gray, Linda Fabiani, Christiania McKelvie, Neil Findlay, Michael McMahon, John Finnie, Drew Smith, Patrick Harvie, Joan McApline, Humza Yousaf, Kevin Stewart, Alison Johnston, Ken MacIntosh, John Pentland, John Mason, Siobhan MacManhon, Kezia Dugdale, John Park, Joe Fitzpatrick, Jamie Hepburn, George Adam, Bob Doris, Patricia Fergusson, Margaret McCulloch, Adam Ingram, Jim Eddie, Mike Mackenzie, Helen Eadie, Elaine Murray, Rhoda Grant, Margaret McDougall, James Dornan, Margaret Burgess, Jenny
Marra, Hugh Henry, Malcolm Chisholm, Sarah Boyack, Aileen McLeod, Colin Keir, Gordon MacDonald, Dave Thompson, Mark McDonald, Clare Adamson, Jean Urquhart, Rod Campbell, Sandra White, Bill Walker, James Kelly, Graeme Dey, Stewart Maxwell.
The Scottish Parliament motion was placed by Jamie Hepburn MSP - Motion S4M-01140. It has been signed by an additional 18 MSPs: Marco Biagi, Maureen Watt, Dennis Robertson, Gil Paterson, Richard Lyle, Bill Kidd, Rob Gibson, David Torrance, Fiona McLeod, John Wilson, Claudia Beamish, Christine Grahame, Paul Wheelhouse, Stuart McMillan, Jackie Baillie, Neil Bibby, Anne McTaggart, Mary Fee.