MPs have cast doubt over the UK government’s readiness for post-Brexit border control checks, which are due to come in next week, arguing that a scaling back of its plans appeared to represent a sixth delay to their long-awaited introduction.

The environment, food and rural affairs select committee (EFRA) has written to the government demanding clarity over the exact nature of the physical inspections on plant and food products, after it emerged these may be significantly scaled back due to fears of delays at the border.

On Tuesday, the government is scheduled to begin checks on medium and high-risk plant and animal imports from the EU, as part of its Border Target Operating Model (BTOM) plan.

However, the Financial Times reported last week that large parts of the risk management system for all commodity groups would not initially be switched on, after concerns within government that the border systems would not be fully ready.

The government insisted that checks would begin but said some would be delayed, with inspectors focusing on the highest risk products before scaling up to a more comprehensive regime in the future.

Robert Goodwill, the chair of the EFRA committee, demanded clarity from the government over what the latest delays entailed and details on what a graduated approach to the sanitary and phytosanitary (SPS) checks would look like in practice.

In a letter to the environment secretary, Steve Barclay, Goodwill said it was clear that ports and businesses were facing further uncertainty and were “confused and frustrated” over the delivery of these essential border controls.

He said: “There is broad consensus that a clearly communicated, phased implementation of SPS checks with distinct, achievable milestones is a strategic and pragmatic approach to change.

“We are concerned that your approach, if as reported, has resulted from poor planning and delivery of the model.”

Goodwill added: “We are concerned that this is a sixth delay to the implementation of SPS import checks in all but name.”