Plans by RBS to close scores of Scottish branches have been branded "economic vandalism" by Labour's Richard Leonard.
The Scottish Labour leader also claimed the reason why the Tory government had not opposed the move was because Chancellor Philip Hammond was "fattening up the Royal Bank of Scotland to sell to his friends in the city of London".
Speaking at a demonstration outside an RBS branch in Aviemore in the Highlands which is among those earmarked for closure, Mr Leonard said: "My grave concern is that Philip Hammond is more interested in fattening the Royal Bank up for a sale to the city of London's institutions than he is to safeguarding services in rural communities like this one."
RBS has put forward plans to close 62 branches in Scotland, although bosses have granted a temporary reprieve to 10 of these, allowing them to remain open until the end of 2018 with an independent review on their long-term future.
However, the Labour MSP said the closures amounted to "the economic vandalism of rural communities" as he criticised the "anti-social behaviour" of RBS bosses.
He insisted there was a "social responsibility" on the bank to provide a service to its customers, particularly "older customers who rely on the face-to-face service that branches like this provide".
Mr Leonard said: "This is not simply a question of economics and politics, it is a question of what kind of society do we want.
"There is a very clear political dimension to this because what this is about is not the economic cost of running branches in Scotland, this is about Philip Hammond fattening up the Royal Bank of Scotland to sell to his friends in the city of London."
He insisted plans to shut the banks were not yet "a fait accompli", arguing: "This is not a campaign about mitigation, this is not about getting a few extra mobile services into communities. This is about opposition.
"The Royal Bank of Scotland is 71% owned by the people of this country and what we want is not just 71% ownership, we want 100% control of the activities of this bank.
"This isn't just a campaign we can win, it is a campaign we must win, must win for communities like this the length and breadth of Scotland."
The demonstration, which was organised by the Unite trade union, comes ahead of RBS chief executive Ross McEwan being questioned on the closure plans by MPs on the Scottish Affairs Committee next month.