Mark Fullbrook, Liz Truss’s new chief of staff, has asserted his grip over Downing Street by bringing senior figures from his lobbying firm into No 10.

The political consultant, a former longtime colleague of the election strategist Lynton Crosby, was appointed to the most senior role in Truss’s team this week, having previously worked on the failed leadership campaign of Nadhim Zahawi.

Senior advisory roles in No 10 have now also gone to Mac Chapwell and Alice Robinson, both founding members of his lobbying firm, Fullbrook Strategies.

The company, which launched in the spring, has lobbied the UK government on behalf of clients including the controversial Libyan parliament and a firm that won a £680m PPE deal in the pandemic.

Two more senior No 10 staff, Beatrice Timpson, the deputy press secretary, and Reuben Solomon, a digital adviser, have done stints at CT Group, Crosby’s political consultancy, where Fullbrook worked for over a decade.

Alongside Fullbrook and his aides, Truss’s inner circle comprises a slew of people who have worked for rightwing thinktanks. Sophie Jarvis, a political adviser, is a former staffer at the Adam Smith Institute, a thinktank working to promote neoliberal and free market ideas, while her economics chief is Matthew Sinclair, a former chief executive of the Taxpayers’ Alliance, a pressure group campaigning for low taxes.

Some senior Tories have raised eyebrows at Fullbrook’s appointment, given his lack of previous experience in government. He has decades of experience in campaigning in the UK and abroad but no prior role in a department.

One former colleague of Fullbrook described him as “avuncular” and someone who had been an asset to Crosby because of the strength of his links with the Tory grassroots.

Fullbrook struck out on his own in March this year after more than a decade of working with Crosby. Crosby sat on the advisory board of Fullbrook Strategies along with Sir Michael Hintze, the Tory donor and Australian billionaire who helped fund a UK-based lobby group campaigning against net zero climate action.

Jill Rutter, a senior fellow at the Institute for Government and former No 10 civil servant, said the chief of staff role could be done in many different ways but was traditionally held by people with some experience of working with the civil service or running a team in opposition.

“Is he clear what the role is and does that person have an ability to create the relationships needed to make that role work? If it’s Mark Fullbrook, does he run No 10 and what is his relationship with the civil servants and does he have experience inside government, or is he basically there to say 50% of the time [Truss has] got her eye on the next election and things should be done through the lens of getting her reelected?

“We’ve had so many incarnations of the chief of staff job, but both [Truss and Fullbrook] will need to be clear on the expectations of the role and how it fits in with all the other roles inside No 10.”

Truss briefed her MPs at the backbench 1922 Committee on Wednesday that her election campaign was already beginning, and that Fullbrook would brief the party on her strategy next week.