The German government has withdrawn approval for the 670m takeover of chip equipment maker Aixtron by a group of Chinese investors, amid concern in Berlin about Chinas growing appetite for German industrial companies.Matthias Machnig, deputy economics minister, told newspaper Die Welt that the government had decided to take back the clearance certificate it had issued last month and reopen a review of the deal after receiving previously unknown security-related information.By late afternoon on Monday, Aixtrons shares had fallen 13 per cent to 5.00 in Frankfurt, less than the 6 per ordinary share takeover offer from Fujian Grand Chip Investment Fund, which is controlled by the Chinese businessman Zhendong Liu. Management has already recommended the offer and, by last week, some 65 per cent of shareholders had accepted it.The decision reflects a growing protectionist backlash against Chinese investment in Germany. Sigmar Gabriel, the economics minister and deputy chancellor, has already backed a proposal to restrict foreign takeovers of EU companies if they involve key technologies that are of particular importance for further industrial progress.However, even under current rules, the economics ministry can review any deal where non-EU investors acquire at least 25 per cent of the voting rights of a German company, and block it if it poses a threat to Germanys public order or security.Deals that involve security of supply in the event of a crisis, telecommunications and electricity, or the provision of services of strategic importance can come in for particular scrutiny, the ministry says on its website.Mr Gabriels initiative, which would greatly expand the governments oversight of these and other deals, is supported by Gunther Oettinger, the EUs digital economy commissioner and a close ally of Chancellor Angela Merkel.He said in a newspaper interview earlier this month that Europes high-tech industry should not just be sold off, adding that other big EU member states such as France and Italy also backed a stronger industrial policy to protect homegrown tech companies.Other countries have also grown more sceptical of Chinese investment. In January, Go Scale, a Chinese private equity firm, was blocked from buying Lumileds, Philips lighting business.German concerns over Chinese takeovers have been rife since Midea, a Chinese appliance maker, bought German robotmaker Kuka one of the countrys most innovative engineering companies earlier this year for 4.5bn.Ministers tried and failed to drum up an alternative bid from a European rival, while Ms Merkel complained about a lack of reciprocity on the part of the Chinese, pointing to the tough restrictions Beijing places on investments by German companies.Germany has become the top destination for Chinese dealmaking in Europe in recent months. Transactions with a record value of $10.8bn were announced in the first half of this year, according to EY, the professional services firm. Chinese investors acquired 37 German companies in that period, compared with 39 in the whole of 2015.A further sign of Chinese interest in German companies came earlier this month when Sanan Optoelectronics announced it had held talks with Osram on a possible acquisition of the German lighting and semiconductor company. Sanan is one of two potential Chinese bidders