Car park operator NCP, which 3i is selling to Australian bank Macquarie, is passing into the hands of private equity for a third time in less than five years amid growing trade union concerns of "venture capitalist asset stripping".

3i, which bought the business from Cinven for £555m (€813m) including debt in 2005, will make about 2.75 times its money in the £790m sale to Macquarie after just twenty months. 3i invested £96m in equity at the time, in its single largest equity ticket to date.