UK construction union Unite has called a decision by the official receiver to make 341 Carillion apprentices redundant an act of "crass stupidity".
With the industry facing a skills crisis, government should have found places for the trainees, it said.
Yesterday The Insolvency Service said the apprentices had been given their notices and would stop being paid at the end of August, the BBC reports.
Training body the Construction Industry Training Board (CITB) has been unable to find placements for them with companies.
The decision to make them redundant was made just as Parliament went into recess last week, preventing MPs from raising concerns at the decision, Unite claims.
When Carillion collapsed in January it employed 1,200 apprentices. The CITB has managed to find placements for some 800 of them.
The decision to make the rest redundant is a further blow to an industry "in the depths of a deep seated skills crisis", Unite said.
"This is an appalling way to treat these apprentices who should have become the backbone of the industry. To dump them and to destroy their training is an act of crass stupidity," said Unite assistant general secretary Gail Cartmail.
She said the government could have used its procurement power to find placements for the apprentices.
That it chose not to demonstrated "that it is not serious about dealing with the skills crisis facing the industry", she said.
She added: "The dismissal of Carillion’s remaining apprentices once again demonstrates that the construction skills crisis will not be tackled until procurement rules are introduced which require that all companies undertaking public sector contracts must train apprentices."
The CITB estimates that the construction industry needs 31,600 entrants every year just to maintain its capacity.
In 2016/17 there were just 21,010 people on construction apprentice courses, Unite said.
Image: Promotional picture from Carillion before it was forced into liquidation (Carillion)