The City regulator is seeking an injunction against the former star fund manager Neil Woodford, claiming he is breaking the terms of a ban related to the collapse of his flagship fund in 2019.
The Financial Conduct Authority (FCA) said on Monday it had started civil proceedings against Mr Woodford and UAE-registered W4.0 - a subscription-based platform.
"The FCA alleges that Mr Woodford and W4.0 are providing regulated investment advice and making financial promotions through the... platform... without authorisation," the watchdog said.
Money latest: New savings account likely to turn heads - but there's a catch
Mr Woodford founded W4.0 as an "investment strategy" community, according to his profile on LinkedIn.
He has been approached for comment on the FCA's claim, which is understood to relate to interaction with UK consumers.
The W4.0 website says in relation to its work: "We exist to explain active investment strategies - with full transparency - so you can see what's inside, why it's there, and the thinking behind it.
"We are not regulated by the FCA or any other regulatory body, and we do not provide financial advice. That's deliberate.
"If you are looking for advice or for someone to manage your money, W4.0 is not the community for you.
"If you want to take back control, make your own decisions, and draw on insight and opinion that supports you in doing so - then welcome to W4.0."
Mr Woodford is contesting the decision notice imposed by the FCA last year, that included a fine of almost £6m and a ban on regulated activity, in relation to the collapse of Woodford Equity Income (WEI).
It was wound down after investors tried to withdraw cash faster than the fund could pay out, amid concerns over its high exposure to illiquid and unquoted shares.
The fund's sale of liquid assets and acquisition of illiquid ones meant WEI was unable to meet rules in place at the time, whereby investors should have been able to access their funds within four days.
The FCA determined that Mr Woodford and the fund "made unreasonable and inappropriate investment decisions" between July 2018 and June 2019.
(c) Sky News 2026: Neil Woodford facing City watchdog injunction
Local news content from CItiblog - read more at 
Ben Stokes and Gus Atkinson face investigation amid 'nightclub incident'
Two arrested on suspicion of murder after boy, 12, dies following Essex vehicle collision
'I've never experienced this level of resentment': Sikh community facing backlash after Henry Nowak murder
Singer-songwriter to the stars Talay Riley stabbed to death in London
Woman, 19, shot dead at Finchley home
