A former Locke Lord London partner who was fired by the firm for using a client account to run a "dubious" £21m investment scheme has been struck off and ordered to pay £70,000 in costs by the Solicitors Disciplinary Tribunal (SDT).

Banking and finance partner Jonathan Denton left Locke Lord in October 2015 after running the scheme for two and a half years, despite concerns raised by enquiries from the FBI and the Metropolitan Police. Last year, the US firm received a record £500,000 fine from the SDT after admitting four failings in relation to its supervision of Denton.

Denton has now been struck off, with an SDT judgment filed last week stating that his actions were "motivated by financial gain" and "a flagrant breach of trust". He was found to have caused significant harm to investors, some of which have since suffered "severe financial difficulties".

The judgment states: "His conduct demonstrated a complete departure from the standards of integrity, probity and trustworthiness expected of a solicitor… his actions were deliberate, calculated, repeated and sustained over a period of time."

The SDT found that Denton had fabricated invoices with the intention of misleading clients and to "facilitate" the payment of money out of the account. Money was also transferred to third parties for purposes not permitted by the trust, with transfers including €550,000 (£483,000) paid to Asociacion Karma Guen, a Buddhist retreat in the Andalusian mountains.

The judgment also criticises Denton for continuing to run the scheme "in the face of concerns expressed by law enforcement agencies both internationally and nationally" including the FBI, the Metropolitan Police Service and North Yorkshire Police. The SDT found that given the number of red flags, it was "inconceivable" that Denton would not realise the dubious nature of the scheme, adding it should have been "even more obvious" to someone with his experience.

Denton did not attend the tribunal, and the judgment stated that he had "failed to deal with his regulator in an open, timely and cooperative manner". It states that in failing to respond, he had chosen to ignore his regulatory obligations, "preferring to protect his position in relation to potential criminal proceedings". North Yorkshire Police has confirmed he faces two charges of fraud.

He was ordered to pay 70% of the costs of the investigation into both him and Locke Lord. The costs reached £119,733, leaving him liable for £76,613, which was reduced to £70,000.

Capsticks disputes partner Daniel Purcell instructed Paul Ozin QC of 23 Essex Street for the SDT, while Denton was not represented.

Denton's scheme began in July 2012 with the incorporation of a company named Ikaya, of which he was sole director and his wife was company secretary, along with a second company, Slonne, which "purported to operate… an investment scheme offering very high yields".

Denton and Locke Lord advised Ikaya "in relation to seven investment trusts during the retainer" between September 2012 and June 2015, during which time Denton billed a total of 1,424.9 hours, delivering invoices from the firm to Ikaya totalling £532,045, $657,194 and €286,902.

Approximately £21m was paid into the firm's client account by investors during that period; however, despite Denton's assurances to investors, the SDT found that "there did not appear to be any verifiable returns to investors".

After concerns over the scheme grew, Denton was eventually fired by the firm in July 2015 and was subsequently arrested at Birmingham Airport in October 2015.

Locke Lord launched in London in 2011 with the hire of a seven-partner team from Salans, with Denton joining the following year from private lender Berkeley House Investments. He is also a former partner at Mishcon de Reya, Salans and Wragge & Co.

Locke Lord's £500,000 SDT fine was double the previous record of £250,000 handed out to White & Case last year for conflict and confidentiality failures.

In March, new Locke Lord London managing partner James Channo told Legal Week it was "an event that no firm wants to go through". He added that the firm had been cooperative throughout the investigation into the Denton episode, and that it has since appointed additional staff to better "monitor compliance" in the London office.

A Locke Lord spokesperson said: "The SRA and Locke Lord cooperatively resolved this matter last year when the SRA accepted our position that the firm and its senior officers did not act dishonestly or with conscious impropriety, or turn a blind eye to Denton's conduct. We understand Denton continues not to cooperate with authorities, but this matter is now only between the SRA, government authorities and Denton.

"We are glad to have put this matter behind us, and again note the matters reviewed by the SRA concerned the actions of Denton and related only to clients for whom he worked. Locke Lord, meanwhile, is pleased with our continued growth in the London market and the multifaceted services we provide our clients."