Analysis of Covid-related contracts worth some £15.5 billion has identified corruption concerns, campaigners have claimed.

The research by Transparency International UK suggests there are questions to answer about the nature of 135 contracts made during the pandemic.

The group points to at least 28 contracts, worth £4.1 billion, which went to organisations with close connections at Westminster, particularly with the Conservatives who were in government during the pandemic.

It also raises concerns about contracts awarded through the VIP lane, a system deemed unlawful by the high court, of which 15 contracts worth £1.7 billion were awarded to politically connected suppliers.

The scale of corruption risk in the former government’s approach to spending public money during the years of the Covid pandemic was profound.

The analysis also raises red flags about contracts which went to “new inexperienced suppliers”, and uncompetitive processes.

It comes as the Covid-19 Inquiry is set to reconvene for its third module, examining the impact of the pandemic on the UK’s health services.

Daniel Bruce, chief executive of Transparency International UK, said: “The scale of corruption risk in the former government’s approach to spending public money during the years of the Covid pandemic was profound.”

He added: “The Covid procurement response was marked by various points of systemic weakness and political choices that allowed cronyism to thrive, all enabled by woefully inadequate public transparency.

“As far as we can ascertain, no other country used a system like the UK’s VIP lane in their Covid response.”

He urged the authorities to “ensure full accountability”, as ministers look to appoint a Covid corruption commissioner.

The report titled Behind the Masks, due to be launched in Westminster on Monday afternoon, recommends ministers investigate the concerns it highlights, bolster its procurement practices and safeguards against impropriety.

A Conservative spokesman said: “Government policy was in no way influenced by the donations the party received – they are entirely separate.”

Rachel Reeves told the Commons in July a Covid anti-corruption probe would go ahead, aimed at clawing back money from Covid fraud.

A spokesperson for the Treasury, which is now leading efforts on investigating Covid era corruption, said: “The Chancellor has been clear that she will not tolerate waste and will appoint a Covid corruption commissioner to get back the money that is owed to the British people.

“The commissioner will report directly to the Chancellor, working with the Secretary of State for Health and Social Care, and their report will be presented to Parliament for all Members to see.”