The watchdog said it was asking five companies to explain claims made in their advertising and on their websites, and give details of their business practices, to make sure they were complying with consumer protection laws.
The call, which followed complaints from consumers, came as Which? Money warned that gold buying companies offered “shockingly bad value” and urged people not to use them.
There has been an increase in the number of companies offering to buy people’s old gold jewellery in recent months, as the price of the metal has soared.
But research carried out by Which? found that the gold companies advertising on television offered people an average of just 6% of the retail price of their gold.
The group sent three pieces of brand new gold jewellery, collectively worth £729, to four groups that promise to buy old gold for cash, as well as to three pawnbrokers and three independent jewellers.
It found the TV gold buyers consistently offered the lowest prices, with CashMyGold offering just £38.57 for all three pieces of jewellery, including quoting just £9.64 for a 9 carat bangle that had been bought for £215, and for which an independent jeweller offered £54.
In another case, Money4Gold told the Which? researcher that a £399 9 carat gold necklace was not gold and demanded they paid £10.95 to have it returned.
Postal Gold increased its offer for all three pieces of the jewellery after the researcher rejected its initial quote, nearly doubling the amount it would pay for two of the items.
Despite this, the quote was still far lower than that offered by pawnbrokers and high street jewellers, who paid an average of 25% of the items’ retail price.
The OFT said it was concerned that consumers’ rights to reject offers and have their gold returned were not being honoured in all cases.
It has not disclosed the names of the companies it has contacted, but said it was considering whether it should change its policy not to name firms at the start of investigations.
Juliet Young, a director in the OFT’s consumer market group, said: “Buying gold using the postal service is a relatively new business model, and while innovation often brings benefits for consumers, we want to check that the market and businesses operating in it are developing in a way that treats customers fairly.”
As part of its research the OFT is also asking consumers who have used the companies to get in touch, although it cannot intervene to resolve disputes between individuals and companies.