Some of the biggest losers among loyal shareholder-customers have been from within the banking sector.

Former Lloyds TSB shareholders, who may still hold shares in Lloyds Banking Group, are being invited to join an action group in a claim for £6billion of investor losses from the takeover of HBOS in November 2008. As in the case being pursued against RBS, it follows the granting by the High Court of a group litigation order.

But unlike the RBS case, there is no cost for small investors to register, as the case is being backed by litigation funders who would take 30 per cent of any settlement. As the six-year time limit for litigation expires on November 19, law firm Harcus Sinclair which is running the case needs shareholders to register by November 12.

Partner Damon Parker said 500 people a day were registering and institutions were showing interest.

But the group would need to represent at least 60 million shares for best results from a claim.

"We are very interested in talking to people about it and hope they will join," he said.

The action group alleges that the bank and five former directors including chairman Victor Blank and chief executive Eric Daniels breached their fiduciary duty to shareholders in recommending the HBOS rescue, and secured shareholder approval on the basis of "misleading information and the concealment of the true financial position of HBOS".

Lloyds Banking Group says: "We do not consider there to be any legal basis to these claims and we will robustly contest this legal action."