U.S. heavyweight Latham & Watkins and transatlantic firm Bryan Cave Leighton Paisner have taken roles on a litigation battle involving British multimillionaire siblings Amit and Meeta Patel.

Claims made in court documents filed earlier this month argue the duo "misrepresented the financial circumstances" of pharmaceutical business Auden McKenzie Pharma prior to its £306 million ($389.1 million) sale in 2015 to pharma giant Actavis Holdings UK.

Bryan Cave Leighton Paisner is advising the Patels and has instructed Paul McGrath QC and Ciaran Keller of Essex Court Chambers.

Actavis and Chilcott UK, which is owned by Actavis, are bringing a claim against the Patels for deceit.

The Patels' former pharma business Auden McKenzie is itself a claimant in the action, arguing Amit Patel acted in breach of his duties as a director of the company.

London-based criminal law boutique firm Byrne and Partners has instructed Andrew George QC and Victoria Windle of Blackstone Chambers, who are acting for the three claimants.

Pharma company Allergan, which merged with Actavis in 2015, is a third party in the action. It acted as guarantor during Actavis's purchase of Auden McKenzie Pharma.

Latham & Watkins has instructed Edmund King QC at Essex Court Chambers to lead for Allergan.

Latham & Watkins is a longstanding adviser for Allergan. It advised on its takeover by Botox-maker Actavis for $66billion (£42billion) in 2014.

Following an investigation by the U.K.'s Competition and Market Authority, the regulator provisionally ruled in earlier this year that Auden McKenzie Pharma broke competition law by overcharging for hydrocortisone steroid tablets from 2011 until its sale four years later.

The claim documents also allege the siblings used the pharma business as a vehicle to pay £13.7 million ($17.4 million) to legal offshore accounts for tax avoidance purposes.