Workers at the Ferguson shipyard in Port Glasgow, Inverclyde, were told of the development yesterday morning.
The GMB union repeated its claims the Government had given commitments about Ferguson's future at the start of the year, saying it could not hide behind EU guidelines on procurement and should ensure commercial work is directed to the yard.
Ferguson's has built two ferries for CalMac in the past three years in a contract worth £20 million, although some work for the Scottish Government-owned ferry firm has gone overseas because of procurement rules.
Jim Moohan, GMB Scotland senior organiser and chairman of the Confederation of Shipbuilding and Engineering Unions, also claimed as recently as Wednesday Scottish Government ministers, including Transport Minister Keith Brown, were making positive statements about Ferguson's future.
Finance Secretary John Swinney has promised a Government task force to find new opportunities for the yard, adding it would "do everything we can to promote a strong future for commercial shipbuilding on the Clyde".
Labour also said it believed Ferguson's was salvageable and that it would work with the SNP to keep it open. Mr Moohan called on the First Minister to meet officers and conveners in an attempt to retrieve the situation at Ferguson's.
A supporter of the Better Together campaign, Mr Moohan however insisted the challenge was not party political but was consistent with the union's position over Ferguson's.
He said: "Alex Salmond needs to step up to the plate, show his mettle. There is work there. It is a commitment of the Scottish Government to have a viable shipbuilding industry. It's in their White Paper. This is a test of the transparency of that."
Staff at Ferguson's turned up to work yesterday to learn most of the 77-strong workforce were being made redundant immediately. Only seven will be retained as a skeleton staff while the receivers try to find a buyer.
Joint administrators KPMG said the business had gone bust due to a lack of orders and mounting cash flow pressure. Union leaders will meet workers on Monday, with the invitation to attend extended to the Government.
Mr Moohan added: "Not to intervene will be an utter betrayal. The Government is well aware of the precarious cliff-edge position the yard was facing and has done nothing to help so far. There can be no hiding behind EU Guidelines this time."
Mr Swinney said: "We will work closely with the administrator to deliver an integrated service to those losing their jobs. We will also convene a task force which will aim to secure new opportunities for this commercial shipyard on the Clyde."
A Scottish Government spokeswoman said: "Higher value public contracts, such as contracts for the construction of ships, are subject to EU law which requires that the contract is awarded without discriminating between bidders and after fair competition."
She added: "During a meeting with the Confederation of Shipbuilding and Engineering Union) on Wednesday Ferguson's was mentioned. Mr Brown advised unions they should speak to the company directly about any concerns."