Another AI firm has recruited from Westminster as the former head of the civil service, Simon Case, joins Invisible Technologies.
Lord Case sought advice from the appointments watchdog on becoming an adviser to the American firm, according to Acoba (Advisory Committee for Business Appointments).
Former prime minister Rishi Sunak has also recently sought advice on his appointment as a senior adviser to San Francisco-based Anthropic, which developed the Claude AI models, and Copilot AI developer Microsoft.
Lord Case, who was once the UK's most senior civil servant, should not draw on "any privileged information available to him from his time in crown service", the watchdog has said.
He should also not "make use, directly or indirectly, of his contacts in Government and/or crown service to influence policy, secure business or funding, or otherwise unfairly advantage Invisible Technologies".
The UK now stands at an important crossroad for high speed rail
It is understood the role as a paid, part-time adviser will not involve contact with Government.
The former cabinet secretary, who sits as a crossbench peer in the Lords after his departure from the civil service in December last year, told Acoba he did not meet Invisible Technologies during his time in Whitehall.
Invisible Technologies is a US company which develops, trains and helps third-parties use AI (artificial intelligence).
Mr Sunak's roles are also paid.
The Conservative MP for Richmond and Northallerton has told Acoba he will donate the payments to his and his wife Akshata Murty's numeracy skills charity The Richmond Project.
Acoba has vetted several appointments over recent weeks before its final closure on Monday.
Its functions are being transferred to the Civil Service Commission.
Former Scottish first minister Humza Yousaf approached the committee to look into his appointment as a global strategic adviser for the Muslim Impact Forum.
The organisation is a "trusted space" where Muslim leaders and institutions "converge to shape agendas, forge partnerships, and deliver solutions that respond to today's challenges with clarity and integrity", according to its website.
Former Conservative rail and HS2 minister Huw Merriman has become the non-executive chairman at High Speed Rail Group.
"I have long championed rail as central to driving economic growth, connecting communities and supporting a more sustainable transport network," he said in a statement.
"The UK now stands at an important crossroad for high speed rail.
"While progress on HS2 since the reset is encouraging, crucial decisions on northern connectivity are still awaited.
"It is vital that these decisions fully reflect the opportunities for improved connectivity, increased capacity and regional growth.
"At the same time, as the UK celebrates the 200th anniversary of the birth of the modern railway, we must learn from recent challenges across the rail industry and ensure new projects are delivered on time, on budget and in a way that maximises both transport and economic benefits."