(Adds quote from DIHK's Wansleben, DIW on Q2 GDP growth)
BERLIN, May 28 (Reuters) - Germany's DIHK Chambers of Industry and Commerce on Thursday raised their 2015 growth forecast for Europe's largest economy to 1.8 percent from a previous estimate of 1.3 percent.
Its survey of more than 23,000 companies showed that business expectations were improving further and that a further 250,000 jobs were expected to be generated this year.
"Growth is picking up, but there is no euphoria because this is an artificially boosted upswing," DIHK managing director Martin Wansleben noted. He added that the main drivers were external factors such as low energy prices and the weak euro.
"And these special factors for the economy are losing steam: The oil price is rising again and the euro has stabilized," Wansleben said.
The DIHK therefore urged the German government to boost public investment and refrain from further legislation that could burden the private sector.
In a separate statement, the DIW economic institute said it expected the German economy to grow by 0.5 percent in the second quarter after expanding 0.3 percent in the first three months of the year.
In 2014 the German economy grew 1.6 percent and it is widely expected to fare better this year -- thanks to solid private consumption as consumers are benefiting from a robust labour market, rising wages and low inflation. (Reporting by Michael Nienaber and Rene Wagner; Editing by Mark Heinrich)