The company said the lawsuit, which was filed in the High Court in October 2022 on behalf of around 3,000 investors in the fund, is the "only route" to claim "the full redress they are owed".
RGL said that anyone who invested in the former WEIF through the platform can join the claim, adding that it is currently preparing a second claim for thousands more claimants who joined the group.
On Thursday (14 December), Link Fund Solution announced that its redress scheme, which was backed by the Financial Conduct Authority, was approved by an overwhelming majority of investors - 93.7% in number and 96.1% by value - at a meeting on 13 December.
Woodford scheme of arrangement approved
According to the FCA's calculations, investors will be able to get back around 77p to the pound, for a total of up to £230m.
As part of the redress scheme, which is subject to court approval with a hearing scheduled for 18 January 2024, investors will no longer be able to pursue any claims against LFS, its parent or associated companies, or submit claims with the Financial Services Compensation Scheme.
However, RGL argued the redress falls short of recovering all the losses suffered by investors in the former WEIF, and noted that claims against Hargreaves Lansdown can still be brought, regardless of the scheme.
The company added it is now the only claimant group pursuing a "full recovery of losses" against the platform, and has urged investors who registered with Harcus Parker or Leigh Day for claims against LFS to join its suit instead, as long as they invested in the fund through the platform.
Remaining Woodford fund assets shrink 40% since last distribution revealed
RGL explained: "The RGL Group's claim is for investor losses sustained as a result of Hargreaves Lansdown's conduct in continuing to recommend the [former] WEIF right up to its highly-publicised collapse, despite Hargreaves Lansdown being aware of the fund's longstanding portfolio diversification and liquidity issues.
"As well as the balance of capital losses yet to be compensated, RGL Group claimants are also claiming damages for the loss of the opportunity of investing in alternative investments that, in contrast to the [former] WEIF, would have generated positive returns."
The group said the total value of its claim is expected to be in excess of £200m.
It added claimants will not bear the costs of the legal proceedings against HL unless it succeeds, and has also secured insurance to protect investors from having to pay the platform's legal costs if the claim is not successful.
In the event the claim is successful, RGL's fee will be of 25%, which it deemed "the lowest of any group formed to pursue WEIF investor losses via court action".
FCA warns against 'unrealistic return' of private Woodford litigation
James Hayward, CEO of RGL Management, said: "Following the result of the vote, we strongly urge any investors who invested in the [former] WEIF via Hargreaves Lansdown to join the RGL Group action, which is already filed in the High Court.
"Now that claims against Link will likely not be possible, the RGL Group's claim against Hargreaves Lansdown is the only route for investors to claim the full redress they are owed.
"Any investors who invested in the [former] WEIF via Hargreaves Lansdown, even if they were previously signed up to a competitor action against Link, are eligible to join. Joining the claim is free and no fees will be deducted until success. The RGL Group book continues to grow daily.
"We believe that Hargreaves Lansdown should be held accountable for its conduct in relation to the WEIF and RGL and our legal team will pursue these claims tirelessly to recover all of the losses suffered by investors."
Hargreaves Lansdown has declined to comment.