BERLIN, April 15 - Germany's six leading economic think tanks will slash on Tuesday their 2003 growth forecast for the country to 0.5 percent and criticise the government for not doing enough to reform the economy, several newspapers reported. Last October, the think tanks estimated GDP growth of 1.4 percent. Frankfurter Allgemeine Zeitung said that the institutes would also forecast Germany's 2003 budget deficit would be 3.4 percent of gross domestic product, busting the European Union's agreed three percent cap for a second year in a row. The institutes are due to formally present their semi-annual forecasts at 0900 GMT.//