Powers to prevent the export of plastic waste to developing countries, binding targets on air and water quality and the protection of wildlife will be enshrined in law under the environment bill due to be introduced in parliament on Thursday.

The commitments will replace the UK’s current obligations on environmental protection under EU law, and the UK will be able to diverge in future from new requirements in EU regulations.

The government has promised to review every two years “significant developments in international legislation on the environment to ensure we keep abreast of developments”, but it will not be obliged to update British law in line with any such developments.

Theresa Villiers, the environment secretary, said: “We have set out our pitch to be a world leader on the environment as we leave the EU, and the environment bill is a crucial part of achieving this. It sets a gold standard for improving air quality, protecting nature, increasing recycling and cutting down on plastic waste.”

While the bill will create a framework for legally binding targets, these targets – such as limits on air pollutants – will not be in place until October 2022 after the government has consulted widely.

On air pollution, the government has pledged an “ambitious” target to reduce fine particulate matter, a lung-damaging pollutant that has been linked to numerous illnesses. But it is not clear whether other pollutants, such as nitrogen dioxide, will be included, and what powers will be available to local authorities to reduce pollution in their areas.

Ruth Chambers, of the Greener UK coalition, said it was not clear that the new bill would strengthen existing protections. “There are continuing concerns that ministers will decide the green watchdog’s budget and board, with a weaker legal status for environmental principles,” she said. “Reviewing international legislation could be helpful, but cannot and should not be seen as a substitute for committing in law to the high standards we already enjoy.”

The new commitment to ban plastic exports to poor countries – an increasing problem for the developing world, as China has closed its doors to plastic for recycling – is the main addition to the bill since its last version under Theresa May’s government, which had to be abandoned during the parliamentary wrangles over Brexit.

However, Libby Peake, of the Green Alliance, said the commitment only repeated the UK’s obligation under the Basel convention, which is independent of Brexit. “The UK already has the power to stop polluting plastic leaving our shores, but has been terrible at enforcing it,” she said. “The Environment Agency has been under-resourced to carry out inspections and carried out only three unannounced site visits in 2017-18.”

The environment bill will join the updated agriculture bill and fisheries bill in forming a new legal framework for environmental protections post-Brexit. For the last four decades the UK’s obligations on these issues have been laid out largely in Brussels.

The bill gives people a greater say in the management of local street trees, which have been the subject of fierce rows in Sheffield and other parts of the country.

It will also enshrine in law the idea of “biodiversity net gain” – that is, when construction or other development takes place, any natural ecosystems that are lost or disturbed as a result will be restored or recreated elsewhere, for instance through tree-planting.