Report from BBC Wales.
While turnover rose by £4m, including £2.3m from reaching the Carling Cup final, other costs increased such as the wage bill and interest on loans.
Some £1.6m was paid out when manager Dave Jones and his staff were sacked in 2011 and Malky Mackay brought in.
The directors said many of the historic financial issues had been resolved.
The losses are an increase on the previous year's £11.8m deficit but the club are currently 10 points clear in the Championship and will hope for a financial boost from reaching the Premier League.
"Since May 2010, the club has seen substantial new investment, principally from Malaysian businessmen, which has continued during the year to the end of May 2012 and thereafter.
"The new investment has stabilised the club's financial position, allowing the club to work towards the delivery of a coherent and sustainable business strategy, as formulated by the new board and its management team."
The directors admitted the immediate future contained "significant challenges" but the Malaysian investors had made further funds available and entered into negotiations with creditors to reschedule payment plans.
"In addition, while their funding is not guaranteed, the new investors have indicated that providing the business develops as planned, they will continue to support the club in the foreseeable future and provide additional finance in order that it can settle its liabilities," said the report.
Increased sponsorship
The club also hopes that the rebranding of the team's main colours from blue to red and incorporating a dragon on the team badge instead of a Bluebird will help secure "future commercial opportunities".
The accounts revealed that the Bluebirds' turnover was £17.5m for the year to last May, compared to £13.6m in 2011.
Over £2.3m of the increased turnover was attributed to the Bluebirds reaching the Carling Cup final at Wembley, which they lost to Liverpool on penalties.
There was also increased sponsorship, including £1m in shirt sponsorship with the club carrying the "Malaysia" name.
But the boost in income was more than offset by increases in expenditure such as the wage bill for players and other staff. This reached £18.5m, up £5m on the figures for 2011.
Increases in administrative expenses and interest on loans also played a part.
The accounts also show that the debt to Langston, the company represented by ex-City owner Sam Hammam, is put at £19.2m, with a one-off payment of £5m due if City reach the Premier League while the debt is outstanding.
http://www.bbc.co.uk/news/uk-wales-south-east-wales-21198131?