Property tycoons donated more than £60m to the Conservative Party over ten years, a new analysis has found.

The sector was responsible for 20% of all donations taken by Boris Johnson’s party between January 2010 and March 2020, with several big spenders handing out millions.

It includes £12m from companies and individuals linked to JCB, the construction company chaired by the Tory peer, Anthony Bamford.

The findings were published in a report by Transparency International, which warned that Tory “dependence” on money from the property sector created a risk of “aggregative corruption”.

It said that the actions and judgements of ministers could be “incentivised by their party’s financial ties to interest groups in this policy area”.

Last year, openDemocracy revealed that more than £11m had poured into the Conservative Party from some of the UK’s richest property developers and construction businesses in the months after Johnson became prime minister.

It came after the Housing Secretary, Robert Jenrick, was accused of “apparent bias” by over-ruling local officials who rejected a Tory donor’s plans for a £1bn housing development and saved his company £45m by fast-tracking the project.

“There is a worrying dependence of the party of government on a small number of wealthy financial backers with relationships to substantial property interests,” Transparency International said in its report, which was published today.

“Although there is no evidence of any direct quid pro quo, ministers’ ability to think bold and think big is likely to be unduly influenced by the interests of their patrons. Weaning them from this dependence is critical to freeing government to explore and implement policy options that will make a substantial, positive difference to housing affordability.”

According to the report, JCB (JC Bamford Excavators Ltd) was the biggest property-related donor between January 2010 and March 2020, with the vast majority going to the Conservative Party.

But other companies linked to JCB have also given millions, including JCB Research and J.C.B. Services.

The JCB business has long had close ties with senior figures in the Tory party. Bamford himself was appointed to the House of Lords in 2013, when David Cameron was in No 10. Cameron had previously recommended Bamford for a peerage in 2010.

A few months before becoming prime minister, Johnson accepted a £10,000 donation from JCB. Three days later, he delivered a speech at the company’s headquarters in which he repeatedly praised it.

JCB also hired the former Brexit secretary, David Davis, as an “external adviser” on a £60,000 salary.

Failed to keep records

Another donor, Bridgemere UK PC, describes itself as a group of companies with “wide-ranging interests within the property and leisure sectors throughout the UK and Europe”. It has given more than £1m to the Conservative Party and is owned via a holding company based in a tax haven.

Last week, openDemocracy revealed how the government had failed to keep any records of how a meeting was set up between Matt Hancock and the chairman of Bridgemere.

Bridgemere owns a “significant stake” in a private health company, Circle Health, that was later awarded a £346.6m COVID contract.

According to Transparency International, the real estate company, Countywide Developments Ltd, is another one of the biggest political donors with links to the housing sector. In its latest account year, it donated more to the Conservative Party than it paid in tax, according to company documents.

Duncan Hames, director of policy at Transparency International UK, said: “While it is no secret that political parties receive much of their funding from a relatively small number of donors, the extent to which the Conservative Party depends financially on those with major property interests is of serious concern.

“Access, and potentially influence, in UK politics remains woefully opaque. We know more about those seeking to shape planning decisions in rural Ireland than we do about private interests trying to shape decisions and housing policy in Whitehall.”

He added: “A major overhaul of the UK’s lobbying rules is needed to increase transparency and ensure there are fewer corners for impropriety to hide.”