Financial Ombudsman Services cases involving networks may now be re-opened after a "game-changing" ruling by the High Court.
Last week in the High Court in London, Mr Justice Ouseley ruled in favour of the Financial Ombudsman Service after Tenet sought to overturn a decision where it had ruled against the network.
An ombudsman had ruled in favour of two of clients that it would be "fair and reasonable" for Tenet to compensate them for the losses the fraudster adviser Alok Dhanda caused them.
But the network disagreed, claiming Dhanda was carrying out unregulated activity beyond the terms of his contract with Tenet, and so he in effect ceased to be one of its appointed representatives.
Dhanda pleaded guilty to 37 charges of fraud in 2014 amounting to losses of £2.9m, and was imprisoned for five years and eight months.
Tobias Haynes, a solicitor at FS Legal, said the High Court decision was a "game-changer" and effectively meant networks could not use private contractual agreements to avoid liabilities.
He said: "We have come across networks whose contracts include lists of products you cannot advise on. Before this case there was no certainty as to whether they were able to do that.
"The usual example is to not advise on unregulated collective investment schemes and the networks say they are not liable but the problem with this is that an unregulated activity is set out in statute."
He said 70 cases had been help up at the Fos by the court case and said his firm had several complaints which had previously been dismissed which he would now seek to have re-examined.
Mr Haynes said his firm would now be seeking to reopen some of the cases where the Financial Ombudsman Service had ruled in favour of the network when an appointed representative has carried out unapproved of activities.
He added that the case would be particularly relevant for people who had been advised to remortgage their properties to invest into investments because it suggested such advice was one and the same.
Mr Justice Ouseley said the central issue was how closely the regulated and unregulated advice Dhanda provided were entwined, and whether or not a "bright or smudgy line" could or should be drawn between them.
He ultimately rejected Tenet's claims that there was a "bright line" between the regulated advice Dhanda provided to the couple to sell a Friends Life policy and the unregulated activity of advising to purchase property in Goa and loan of the money to him.
Mr Justice Ouseley said Tenet's position would effectively mean that appointed representatives could advise their clients to sell their regulated investments and put their money in a "Ponzi-fraud" without their networks having any responsibility for this.
Caroline Bradley, Tenet's group risk and regulatory director, said the network has personal guarantees in place for advisers, claiming this means they are personally liable for any business outside of their authority.