The 'alternative remedies package' was part of an agreement made with RBS after it was bailed out by the government following the financial crisis.
The package was created in 2017 after original plans to hive off a group of RBS branches as an independent bank proved unworkable, which led to this week's announcement that RBS will close 162 branches and axe 800 jobs.
Lansons is understood to have been appointed to handle press relations and media strategy.
The agency was unable to comment on the news and PRWeek has not heard back from HM Treasury regarding the appointment.
Today the Treasury said it has appointed Godfrey Cromwell and Brendan Peilow as the BCR's executive leadership team.
Under the terms of the remedies package, RBS will pay £425m to smaller banking rivals to encourage investment into new services, while £350m has been allocated to encourage RBS's customers to switch banks. The package will be launched over the coming months.