British Prime Minister Theresa has promised to eradicate avoidable plastic waste by 2042, as part of a "national plan of action" she hopes will show that her government is about more than just Brexit.

On Thursday May unveiled a new environmental agenda, which she said was now "centre stage".

May is keen to put divisions over leaving the European Union, scandals and an ill-judged election behind her and try to broaden the appeal of her Conservative Party.

While welcomed, her moves to extend a 5 pence charge for a single-use plastic bag to all retailers, to have packaging-free aisles in supermarkets and to create a new Northern Forest were also criticised by some lawmakers for not going far enough.

She told an audience in west London that her party had made an important pledge "to make ours the first generation to leave the natural environment in a better state than we found it".

Her Environment Minister, Michael Gove, who ran against May in a 2016 leadership contest, has introduced some green policies: protecting bees by restricting some pesticides and banning microbeads.

But the latest moves were described as "vague" by the Green Party's Caroline Lucas.

"Focusing on only the low-hanging fruits of environmental protection is like treating heart disease with a bypass, without changing your diet or taking up regular exercise," she said in a statement. "It's not a serious, sustainable solution for the long term."

May, who said she regularly recycles and has barn owl, bat and bird boxes in her garden, said she would look at plastic bottle deposits and would launch a call for evidence next month on whether to impose taxes or charges on single use plastics.

Worries about overuse of 2.5 billion disposable coffee cups each year have also been raised by campaigners. Parliament's environmental audit committee last week called for a 25 pence "latte levy" to be charged hot drinks.