The European Central Bank says the cost of its new Frankfurt headquarters will jump by as much as 41 per cent due to higher prices for construction materials and "a number of unforeseen challenges". The 185-metre twin-tower building would cost as much as €1.2 billion (HK$12.07 billion), up to €350 million more than the initial price of €850 million, the ECB said. The relocation to the new premises remains scheduled for 2014. The cost blowout comes as the bank castigates European governments for failing to control their own spending. It is also another setback for a project that was delayed in 2008 when all of the bids to build the towers exceeded the ECB's budget in the initial tender process. The building was originally scheduled for completion last year. "It is anticipated that increases in the price of construction materials and construction activities from 2005 until the completion of the project in 2014 will lead to a €200 million increase in the overall investment cost of the buildings," the ECB said. "In addition, there have been a number of unforeseen challenges that needed to be dealt with that are likely to account for additional costs of about €100-€150 million." The ECB revealed the new costs at a "topping out" celebration to mark completion of the main structural works on the building. The complex on the banks of the Main River features two twisting towers connected by an atrium. One tower reaches 185 metres, or 45 floors, and the other rises to 165 metres, or 43 floors. It is built on the site of Frankfurt's former wholesale fruit market, and will include a memorial to the Jews who were detained there during the Nazi era before their deportation to concentration camps.