The OFT has warned that it plans to take severe action against high street stores and online retailers who break the law by not making price offers clear.
One common practice the OFT is particularly worried about is "drip" pricing, where compulsory costs, such as delivery charges, are added during the buying process.
We found one man who fell foul of these schemes.
Dave Thick-Prannock, 35, of Hinckley, thought he'd found a bargain when he browsing for DIY gear online.
"I came across this site advertising home security at 'throw-away' prices.
"Well, I thought the offer of an ex-Soviet inter-continental ballistic missile for £47.50 plus VAT was just too good to miss - I mean, what better way to deter burglars and robbers than a 200-megaton thermo-nuclear device? They certainly wouldn't bother you a second time.
"Anyway, I paid through PayPal and got a receipt via e-mail.
"But a couple of weeks later when a huge truck and trailer with a rocket on the back pulled up in our street, the guy handed me a bill and demanded payment there and then.
"It seems the £47.50 plus VAT was just for the missile!
"They wanted £87.25 million for 'acquisition' - whatever that was - £750,000 for the computer guidance program, £3 million for the access codes, £5 million for fuel and £4 million for transport!
"And they were just going to leave it parked out front! They'd really chewed up Mrs Limpet's lawn coming round the corner.
"Well I handed over the credit card, but I'm really cheesed off that the 'extras' weren't mentioned in the ad."
A spokesman for the OFT said: "This is precisely the kind of thing we are warning people to be wary of.
"And we feel Mr Thick-Prannock was done over the fuel."