Warnings have been issued to parents who use machines to dispense pre-warmed baby formula.

Tommy Tippee issued an alert after parents reported problems with the “Perfect Prep” machines - which are designed to dispense pre-mixed baby milk at the perfect drinking temperature.

One Portslade mum said she had found what she believed was mould in the pipes of the machine she used for her baby's feeds She said on facebook: “I thought I would check mine and I can see mould all in the tubes." she urged parents to check their machines saying her daughter had suffered from bronchitis at five week's old.

She added: "Mine's in the bin already. Let people with them know.”

Tommy Tippee issued a statement saying: "We were very concerned by these findings and started an immediate investigation. To help us, we’d like any parents who have found similar build-up in their Perfect Preps to contact us as soon as possible, so we can arrange to have their machine and filter returned to us via Freepost for examination by an independent laboratory.

"Until they’ve been examined, it’s impossible to determine the exact cause.

"However, our preliminary investigation has found two things. Firstly, the build-up we’ve seen so far we suspect is carbon residue and not mould. Carbon is a harmless, inert bi-product of the filtration process. Secondly, some parents have told us they’ve used ordinary water jug filters instead of the Tommee Tippee filters. Standard filters do not contain the ultra-filtration membrane needed to remove bacteria, plus are more likely to release carbon into the system.

"Although we can’t be certain until we’ve received back and examined more machines, it is possible these factors are linked to what people are seeing. However, the investigation will continue until we’ve found answers.

Anyone with any questions or concerns about Perfect Prep can contact us via our Careline on 0500 97 98 99 or our Facebook page."

NHS guidance also states that the machines may not mix baby milk in the sterile conditions the Department of Health would recommend.