Defra said on 28 June that action is being taken by the UK Plant Health Service to eradicate late June findings of OPM in Hampshire, Warwickshire and Gloucestershire, including surveillance, tracing work and destruction of both the caterpillars and infested trees.
Gardiner, launching the RHS Hampton Court Palace Garden Festival 'Year of Green Action' garden, told Horticulture Week OPM can only be stopped "through national measures, through legislation - that's how we'd have to address bringing in further controls.
"We already have controls, but we will review how this came into other parts of the country beyond London when we shouldn't be importing OPM. It's as simple as that. I won't be ruling anythng in or out. We need to be looking how we best address this problem.
He added: "I am very concerned indeed about OPM. It's one we are seeking to contain in London and part of the south east so we can find what is the best way of dealing with it. That is why I'm dismayed to find OPM in imports and why those oaks have to be destroyed and I think it's irresponsible of suppliers to be, with the requirements we've taken by way of national measures on importing oak trees, to find that some have got through with OPM, so I will be considering how best we can deal with this because it is imperative we do not spread OPM.
"It is why we have some of the most extensive Protected Zones, precisely to contain it within London where it unfortunately arrived in an import [in 2005] and we should have dealt with it immediately then. I regret it wasn't dealt with with the vigour we should have.
"I'll be looking to see what measures are possble to escalate the fact that no imports of oak trees should, be coming in where there's a risk of OPM.
"This costs people who in good faith buy trees form importers and have been told they are safely sourced and if not they have to be destroyed and the person who planted them in good faith will need to seek legal redress.
"I will reflect on this with urgency. I'm actively considering following the latest news on OPM, and being sent beyond London, is not satisfactory and will seek ways of stopping this.
"We've had two incursions when it shouldn't have arrived and it's my responsibility to look to see why. We should be heightening biosecurity to protect oaks and owners from what is a considerable concern. You would not want children and adults around it with the toxicity of the caterpillars.
He said he would act "as soon as possible" because it is "imperative we save the oak trees of this country from OPM".
Lord Gardiner said Action Oak could help find ways to deal with OPM. But at the moment, the best way to stop it is "through controls any imports and you buy grown in Britain".
He added: "Biosecurity is absolutely key to everything we do. In this country and across the world we need to be much more recognising of stopping pests and diseases of coming, yes, to this country, but crossing continents and we need to heighten not only our own national arrangements but across the world the message in the year of plant health (2020) is about how do we ensure that pests and diseases are not spread which is why if we are a country which has more protected zones than anywhere in the EU, which is why we take national measures."
He said Defra had acted through increasing resources and its Don't Risk It awareness-raising campaign and on Xylella and Emerald Ash Borer "we have been in the vanguard of raising protections". He called for more international working together and praised the work of chief plant health officer Nicola Spence.
"Biosecurity is a global concept because it is not acceptable in my view for plants to be sent to this country with pests and diseases, whether its from the EU or whether its from further afield."
The Year of Green Action garden was created together with young people with disabilities and the Sensory Trust, the garden will take visitors of all abilities on a journey through the senses, with plants specially chosen for their multi-sensory qualities.
Scent, touch and taste are all appealed to with the furry leaves of woolly thyme, while the velvety leaves of senecio ‘angel wings’ are for children to touch and feel. The garden is decorated with ceramic tiles designed by children with disabilities and their families.
The Year of Green Action garden will also ask visitors to pledge to help improve the environment so we become the first generation to leave it in a better state than we found it – a key objective of government’s 25 Year Environment Plan.
Environment Secretary Michael Gove said: "The Year of Green Action garden is a demonstration of the role gardens and other outdoor spaces can play in sparking joy for nature in all children.
"Now more than ever it is vital that we ensure that the next generation is engaged with the environment, not only for their own health and well-being, but for the health and well-being of the natural world itself.
Helen Rosevear, co-designer of the Year of Green Action Garden, said: "Family gardens give children one of their first opportunities to connect with nature, and the Year of Green Action garden shows how we can all create spaces for everyone to enjoy while being mindful of how they can benefit wildlife and the environment.
"Family gardens, schools and other organisations can create features such as dens, sensory domes and bug hotels, but on a smaller scale we can all choose plants that have a multi sensory appeal as well as being attractive to wildlife.
"Research shows spending just two hours a week in nature shown to have incredible benefits on health and wellbeing. That is why the government launched its year-long drive – the Year of Green Action – to help everyone get involved in projects that support and enhance nature. By designing the garden to be accessible for all, it will help improve access to the natural world for children of all abilities.
"Visually, the garden moves from mixed, stimulating colours of sunflowers and sweet peas on the patio and pollinator area to more calming blues and purples of lavender. The paths and surfaces created from recycled shredded rubber to create a firm but forgiving surface for children.
"There is a sensory dome to provide a quiet reflective space, especially valuable for children with additional needs, while a covered craft area provides a space for the whole family to engage in nature based activities and play.
"The garden is also environmentally friendly with integrated water storage and composting, plants that have been specially chosen for both their low water demand in order to reduce water use and their attractiveness to pollinators, and permeable paving to allow water to percolate and prevent flooding.
Claire Francis from the Sensory Trust said: "We are delighted to be co-designing this Year of Green Action garden and hope that it inspires many people to use our simple, low-cost techniques to create deeper, lasting connections with nature in their own garden."
The creation of the garden comes midway through the government’s Year of Green Action forming a part of the Government’s 25 Year Environment Plan, where individual and businesses are being encouraged to do more to help nature and the environment. The Government has pledged £10 million to help children from disadvantaged backgrounds better access the natural environment.