Lord Young, the IoD president, opened proceedings at the Albert Hall by saying that the business community would live with whichever party was in power on 2 May adding "and may the Lord have mercy on all our souls".
He refused to be drawn into openly criticising Labour but said that an increase in corporate taxation had to be on the agenda if it came to power.
Tim Melville-Ross, the institute's director general was less inhibited, attacking key elements of Labour's manifesto and warning of the uncertain future Britain would face under Labour. "There is so much uncertainty about what a new Labour government would do that really it has to be resolved as soon as possible. Are they for privatisation or against? Are they for a single currency or against?"
He also criticised Labour on its support for the social chapter and the windfall tax which he described as "retrospective, perverse, and introduced for the wrong reasons".
However, Mr Melville-Ross also took the Conservatives to task, saying that a re-elected Tory government would be "a long way short of perfect".
He said there were real concerns about the way the Tories had managed the economy and the size of the borrowing requirement, nor did the IoD suppport Tory proposals for further industrial relations legislation to give the public the right to sue unions which held strikes in essential services.
Mr Melville-Ross said that, whichever party won power, interest rates were likely to go up to take the heat out of the economy. There was also likely to be a tightening of fiscal policy to keep a lid on consumer spending.