Analysis by Guardian and Friends of the Earth raises questions about impartiality in post-Brexit reform

Dozens of MPs and peers, including some with vast inherited wealth, own or manage farms that collectively have received millions of pounds in European Union subsidies.

An analysis by the Guardian and the environmental group Friends of the Earth identified 48 parliamentarians who claimed £5.7m in farming subsidies under the EU’s common agricultural policy (CAP) in 2017, the latest year for which figures are available.

The largest single payment – £473,000 – was paid to a Sussex farming firm run by the 18th Duke of Norfolk, a large landowner whose estate dates from the middle ages.

Conservative MP Richard Drax, descendant of a 19th-century slave-owner and current resident of the family ancestral seat of Charborough House in Dorset, owns a farm that received £411,000.

Table Sum of EU CAP payments in 2017 shows data as recorded in official database. The Guardian also asked each parliamentarian what financial benefit they derived from the farm in 2017

Matt Ridley, the fifth Viscount Ridley, runs two firms which received £316,000. The Blagdon estate in Northumberland has been owned by his family since 1700. The hereditary peer was forced to resign as chairman of the Northern Rock bank in 2007 after presiding over its financial collapse.

British farmers will no longer receive subsidies from the EU after Brexit and will instead be paid by the UK government. The EU subsidies have been criticised for many years for rewarding large landowners, who receive the biggest payments. The top 10% of recipients receive almost 50% of total payments, which in the UK amount to £3bn per year.

The environment secretary, Michael Gove, is proposing to change the system to ensure future payments help to create “a cleaner and healthier environment”. The bill to implement this change is going through parliament.

Campaigners have raised questions over whether politicians will be swayed by their financial interests and seek to influence the bill. The politicians have declared their financial interests in an official register as required under the parliamentary rules.

The minister responsible for piloting the bill through the House of Lords is junior environment minister, Lord Gardiner of Kimble. He is a partner in a family farm, CM Robarts & Son, which received £49,000 in EU agricultural subsidies in 2017.

Asked what measures were in place to avoid a clash of interests, the Department for Environment, Food and Rural Affairs said: “All ministers are required to make known any relevant interests known to them which may be thought to give rise to a conflict.”

It added that Lord Gardiner had declared this interest and that, as with other ministerial interests across all departments, it had been published by the Cabinet Office.

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Three other members of the government have farming interests. Lord Taylor of Holbeach, the chief whip in the Lords, has a shareholding in a firm that grows cereals, crops and vegetables which had an EU subsidy of £159,000 in 2017.

Taylor, who was a junior minister in the agriculture department between 2011 and 2012, said he had “disclosed everything in accordance with the requirement of the House of Lords code and ministerial code” and had no further comment to add.

The Conservative MP for Sherwood, Mark Spencer, a government whip, is a partner in a Nottinghamshire farm which received an EU subsidy of £14,000 in 2017. In the House of Commons register of financial interests, he declares that he receives “benefit in kind from the farm of £5,000-10,000 per annum in the form of payment of telephone, heating and council tax of my family home” and performs “a maximum of 80-100 hours per year of otherwise unremunerated work on the farm”.

A farming firm owned by junior education minister Lord Agnew received a subsidy of £212,000 in 2017.

Guy Shrubsole, a Friends of the Earth campaigner, questioned whether the politicians would have their own financial interests or the public interest uppermost in their minds when they came to vote on reforming the subsidy system. He said: “We hope that politicians will put the public interest first and vote to radically overhaul farm subsidies so that, in future, public money goes to pay for public goods, like restoring nature and reducing flooding.”

The list of payments has been compiled from the declarations of financial interests – such as land ownership and company directorships – made by MPs and peers in parliament and the official database of EU payments in the latest available year (up to October 2017) that is published by the government.

Facebook Twitter Pinterest Arundel Castle in Sussex, seat of the Duke of Norfo0lk, who received the largest single payment from the EU. Photograph: Guy Nicholls/Getty Images

Although MPs and peers make public their financial interests, they are not required explicitly to declare if they are financially involved in a farm or agricultural enterprise which receives CAP payments, nor how much is received.

Some of the politicians declined to say if they drew any sort of income from the farm. Others said that, like many other farmers, they did not make a profit and the subsidy enabled them to keep the farm afloat and people in work.

The Duke of Norfolk is a director and largest shareholder of Norfolk Estate Farms Ltd. He said he had not received any financial benefit from the firm for many years.

He said: “For the last 10 years, the main thrust of the farming operation has been to try and find a middle way between sustainable food production and reversing the decline in many red-listed species of birds, broadleaf weeds, wild flowers and insects which used to be plentiful on arable farmland.”

Ridley said: “I have argued against subsidies for farming in general – even though this is against my personal interest in the short run – but that some allowance may need to be made for the way British farmers are restricted in how they can farm competitively because of environmental and other rules.”

Drax did not comment.