Chris Walker, head of housing and planning at the think tank Policy Exchange has dismissed capping rents, saying landlords could potentially leave the housing market altogether.
Capping rents could potentially lead to landlords simply withdrawing from the market, if they don't get the price they need to make their investment economically sound.
Ahead of party's campaign for the European and local elections, Ed Miliband has pledged rent controls such as banning letting agents charging tenants fees and introduce three-year tenancies, if he came to power.
More top news
Police have arrested three teenagers and a man following the shooting of a three-year-old girl with an air gun.
Police have released new images of the site of the fatal crash near Shoreham Airshow in which at least 11 people died.
Ministers have deployed a new weapon to combat Islamic State - a dedicated Twitter feed.