An assessment of the seas around the UK will carried out by the government and made available online, the Department of Environment Food and Rural Affairs (Defra) has promised, with a view to cleaning up and improving the inshore environment.

Thérèse Coffey, a Defra minister, said that by the end of this year “a major assessment of how our seas have moved towards good environmental status” would be completed. This assessment, which would be accompanied by an online tool that the general public could use to examine progress on the marine environment and the pressures it is under, is expected to inform future marine policy.

Licensing and planning systems for coastal and marine areas will also be overhauled. This could affect coastal developments, including those of potential offshore wind sites.

She also said a full series of marine plans covering the whole of the UK’s coast would be completed by 2021, and said that the UK’s often-overlooked coldwater coral reefs would take precedence this year, which has been designated international year of the reef.

With Brexit looming and little detail so far on what fishing policies might replace the EU’s common fisheries policy in UK waters, Coffey promised that long term sustainability would be paramount. However, she admitted that only 30% of the fisheries exploited by the UK were currently within sustainability limits. She gave no indication of what level of exploitation a post-Brexit fisheries plan would allow, and concentrated her comments instead on species that are not generally used for food.

Coffey said: “The proportion of large fish in the North Sea has climbed steadily since 2010 to levels not seen since the 1980s. We must still seek to ease the impact of human activity, however, particularly on seabed habitats and fish populations. An ecosystems approach to fisheries management will account for, and seek to minimise, impacts on non-commercial species and the marine environment generally, including through technical conservation measures.”

The minister also repeated plans, set out by the Commonwealth secretary general Patricia Scotland last year, for a “blue charter” for Commonwealth nations, to be adopted at their meeting in April. This will involve commitments on the reduction of plastic waste entering the seas from Commonwealth countries.

Coffey was speaking at the Coastal Futures conference in London, a long-running annual event focusing on marine management.