He added: “The city has a lot of students and Polish workers who live in multi-occupied properties. I’m worried that rather than chase after persistent offenders, they will soon move on to easy targets, like families.

“If my daughter, say, put a tin can in the bin, what am I meant to do? Do I have to root through the rubbish to make sure there’s nothing out of place?”

Sally Richards, from St Budeaux, said: “You can’t always recycle everything. My nine-year- old and 11-year-old love to recycle but sometimes the odd crisp packet and ice pole wrapper falls through the net and ends up in the wrong rubbish.

“If I am going to have to pay a fine for that, what on earth are we coming to.”

Labour councillor Chris Pattison said: “It sounds a bit draconian and intrusive to me.

“What right has someone got to ask whether you have any children or how you look after them?”

The move in Plymouth follows Exeter city council’s failed attempt to prosecute a woman for putting the wrong items in her recycling bin. Exeter spent around £6,000 bringing the case to court, but could not prove beyond reasonable doubt that the woman was personally responsible.

Lawyers doubted whether Plymouth’s proposed “bin manager” nomination would succeed.

Cathryn Smith, a partner at Foot Anstey solicitors, said it would not constitute a contract but could be used as evidence that someone had accepted responsibility. “If you don’t sign it, the council would still have to prove who is responsible.”

Plymouth’s environment chiefs said: “This will send a clear message of zero tolerance.”

A city council spokeswoman added: “The letter, which has not yet been approved, may also include a questionnaire, which would have more detailed questions such as how many people are in a household and whether they have any medical needs that we should take into account which will enable us to help them rather than prosecute them.”