Edinburgh City Council's troubled city-centre tram project faces a seven-month delay – and could now breach its £545m budget. The project's developer has revealed it is in dispute over costs with the construction group, led by the German firm Bilfinger Berger. A row between the two groups has already led to a month-long halt to work on Princes Street in the city centre, and the issue is now unlikely to be resolved until later this year. The construction consortium has been concerned at the number of design changes within the project, which it claims has driven up costs. The council said completion of the tram project was now forecast for February 2012, seven months later than planned. Commenting on the dispute, Steve Bell, tram project director for the council-owned tram firm TIE, said: ‘The firm's behaviour has been really disappointing. We do not expect an international contractor to behave in such a manner.' He also warned the project could even be completed ‘beyond 2012, if we don't resolve the problem'. According to local media reports, Edinburgh council will this week discuss a new report on the project, in which council chiefs admit it will be ‘very difficult' to complete the ‘full scope' of the line within its budget. Some council sources have suggested the tram route could be curtailed and might not now run between Edinburgh Airport and Newhaven.