More than 250 university students have been unable to move in to their accommodation because of delays to a £30m development.
Portsmouth University students were told they could not move in to the 17-storey Stanhope House, days before the start of the academic year.
Prime Student Living apologised "unreservedly" for the "disappointing, concerning and distressing" delay.
The university said it was "working to secure alternative accommodation".
One third-year student, who wished to remain anonymous over fears his tenancy agreement could be terminated, said he felt "betrayed" after paying £2,800 for a studio flat for a term.
He received an email on Saturday telling him completion had been delayed by a "short period", shortly after contacting the firm himself with concerns the building did not look ready.
"Prime Student Living expected Stanhope House to be ready ahead of the start of the academic year, but circumstances have now changed," the email said.
"Whilst this is out of our control, we unreservedly apologise for what is very disappointing and concerning news."
He has since been placed in halls of residence.
He said: "It's been terribly mismanaged. They were ignoring and denying issues until the very last minute."
Prime Student Living managing director Steve Goldstraw said: "We have been taking a number of actions to source temporary alternative accommodation solutions in the short term whilst construction at Stanhope House is finished.
"There are a number of students for whom Prime Student Living have not been able to source accommodation that meet their needs, so we have referred these to the University of Portsmouth who are providing assistance to help find accommodation."
The problems follow delays to the company's 310-bed Coppergate scheme in Swansea which also left students looking for alternative accommodation.
The central Portsmouth development was advertised as having 138 studio apartments and 118 en-suite flats, with charges of up to £10,600 a year.
The university said it was confident it could find alternative accommodation for 64 students who had not been re-housed by the company.
Many are freshers who are due to start university next week.
University vice-chancellor Graham Galbraith said concerns were raised about the progress of Stanhope House with Prime Student Living in July.
He said: "We were reassured they had everything under control.
"We have no control over them and cannot insist they do things for us, but it is a very irritating situation that was predictable."