The Conservative MP Owen Paterson faces a 30-day suspension from the House of Commons for an “egregious” breach of lobbying rules, raising the possibility he could lose his seat if enough constituents trigger a byelection.

The MP for North Shropshire, a former cabinet minister, was found by the Commons commissioner for standards, Kathryn Stone, to have breached paid advocacy rules, after it was discovered he had worked as a consultant to Randox, a clinical diagnostics company, since August 2015. It was also discovered he was a paid consultant to Lynn’s Country Foods, a processor and distributor of meat products since December 2016.

In a ruling handed down on Tuesday, the commissioner found he made three approaches to the Food Standards Agency relating to Randox and the testing of antibiotics in milk; seven approaches to the same agency relating to Lynn’s Country Foods; and four approaches to ministers at the Department for International Development relating to Randox and blood testing technology.

Stone said he had failed to declare his interest and used his parliamentary office on 16 occasions for business meetings with his clients between October 2016 and February 2020, and sent two letters relating to his business interests on taxpayer-funded Commons-headed notepaper.

She called it “an egregious case of paid advocacy” and said Paterson had “repeatedly used his privileged position to benefit two companies for whom he was a paid consultant, and that this has brought the house into disrepute”.

The standards committee ruled Paterson should be suspended from the Commons for 30 sitting days.

Under a law introduced in the wake of the MPs’ expenses scandal, any MP suspended for more than 10 days can face a trigger ballot where their constituents decide whether to force a byelection by supporting a recall petition. Ten per cent of the electors in Paterson’s seat would need to support the petition for a byelection to be called.

Paterson has previously served in two cabinet posts – including as secretary of state for environment, food and rural affairs.