The independent report said that inadequate emergency plans were in place when six trains broke down in December, leaving 2,500 passengers stranded in the Channel Tunnel.
Heavy snow in northern France caused the trains to lose power.
The report said that the trains "had not undergone sufficient weather preparations" to withstand "extremely severe" weather conditions.
It also said passengers had been let down by poor communication
"Provision of information to passengers in stations, through the call centre and via the website was not satisfactory", the report found.
It recommended that trains should be made more reliable to cope with severe weather, and improvements to the management of train evacuations and delays be made.
The report added: "First, passengers need to be assured that the Eurostar trains are reliable and so improvements need to be made in this area as a priority.
"Second, if a train breaks down and passengers have to be rescued or evacuated, this must be done with greater speed and consideration, and more comprehensive emergency plans should be put in place.
"Third, in an emergency, passengers need to have prompt information and regular updates.
Eurostar must improve the way it communicates with passengers and put in place new systems and practices to achieve that."
The report – which was commissioned by Eurostar – was drawn up former GNER East Coast Main Line rail chief Christopher Garnett and French transport expert Claude Gressier.
Eurostar said in a statement it accepted that the way it dealt with the disruption was unacceptable.
It added: "We are very sorry for the inconvenience and discomfort that we caused to our passengers."