It is all very well Mr Cameron coming up with grand plans, but since he came to power, fewer illegal immigrants have been stopped at our borders, fewer foreign criminals have been deported and more people have absconded from Heathrow airport.
He said it could discriminate against people who genuinely want to visit for a short period but are too poor to pay the deposit, while "unscrupulous people" who can afford it may be willing to "fork out their one or two thousand pounds" in order to circumvent the system.
Shadow immigration minister Chris Bryant said: "It is time that the Home Secretary came clean about the security at our borders.
"Her cuts to staff have seen passport queues lengthen, not only leading to delays for passengers but also leaving UK Border Force staff with a difficult decision of whether to relax security to alleviate congestion and risk allowing people to enter the UK without being properly checked.
"With a cut of over 5,000 staff promised by the next election, the Home Secretary is leaving our borders dangerously understaffed, just when the UK is expecting record numbers of arrivals for London 2012."