Piasecki is thought to be searching for new business challenges after resigning as chairman of the Baugur-owned retailer Goldsmiths last month.
He held this position for 24 years, but was understood to have left after a boardroom bust-up.
Ratner is in talks to launch a web, home shopping and high street jewellery business with Indian partner SB&T and wants to recruit some high-profile non-executive directors.
He is keen to buy a 20- to 30-store jewellery chain to complement his jewellery site Geraldonline. Ratner said the latter will be upmarket and the high street chain will be mainstream.
He said: “About 80 per cent of what we’re selling online is diamond rings, but no one buys£10 earrings on the internet.”
Ratner would become chief executive of the new company, which he intends to float on AIM.