More than 2,000 workers at UK parcel delivery firm City Link were told by the firm on Christmas Day that they would lose their jobs.

City Link notified its staff in an email on December 25 that they would be out of a job on New Year's Eve as the company was going into administration after years of substantial losses.

Investment firm Better Capital, which bought City Link for £1 in 2013, said it regretted the decision, but defended the timing of the announcement, CNBC reported on Tuesday.

The announcement was supposed to be withheld until the day after Christmas Day, but Better Capital said it released the statement early after a whistleblower leaked news of the redundancies.

"Unfortunately the appointment of an administrator was leaked to the media ahead of the intended announcement. The directors very much regret the impact on the employees of City Link receiving such bad news on Christmas Day," it said in a statement to shareholders on Monday.

RMT, a transport union in the U.K., has lambasted the company over recent days after meeting with City Link's administrators Ernst & Young.

The RMT called it a "truly horrific catalogue of mismanagement" and accused City Link of not telling staff that it had been working with insolvency advisors since November.

The founder of Better Capital, venture capitalist Jon Moulton, told the Financial Times on Monday he had lost "several million pounds" of his own money in City Link and had explored "every possible way" to save it.