A Defra representative said: "If the problem takes hold around Cambridge, the iconic and traditional pastime of punting may have to be stopped due to the health and safety risk of a punting pole or boat getting tangled in floating pennywort.
"Additionally, when thick mats of this species form it can be hard to distinguish between where the river bank ends and the water begins. There is a risk that animals and humans may mistake it for solid ground and fall through into the water."
Removing the plant from waterways costs the Environment Agency £120,000 per year.
Darren Trumper, operations delivery team leader for the Environment Agency, said: "Floating pennywort has become such a problem in the River Cam and the washes, that we now have to decide the priority areas to tackle, in order to allocate the funds available.
"It has been decided to try to eradicate the floating pennywort at the start of the river to the confluence of the River Lark.
"An especially worrying factor in the infestation is the invasion of the River Cam washes, which is a Site of Special Scientific Interest (SSSI) and crucial to all kinds of wildlife.
"The still waters provide the perfect breeding ground for floating pennywort which has formed dense mats that block out oxygen and light for fish and also deprive all kinds of birds and creatures from feeding from the waters."
Defra and the Scottish Government launched the Be Plant Wise campaign last month highlighting that gardeers should not dump "five of the worst offenders currently wreaking havoc on our wildlife and waterways":
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Sclerotinia sclerotiorum, S. minor and S. trifoliorum particularly affecting legumes such as green, broad and faba beans.
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