Efforts to set up a network of protected areas around the UK's seas have been delayed, the government admitted today.

Environment minister Richard Benyon said the government was still fully committed to creating "marine conservation zones" in UK waters, but there were a "number of gaps and limitations" in the scientific evidence for the 127 proposed areas.

But conservationists criticised the delay as "unacceptable" and warned the government was failing to protect important habitats and wildlife.

In a written ministerial statement, Benyon said that government bodies Natural England and the Joint Nature Conservation Committee (JNCC) would be providing their advice to government on the proposed zones six months later than planned.

A public consultation on all the sites would be conducted towards the end of next year, with the first conservation zones designated in 2013, he said.

Some 127 proposed marine conservation zones (MCZs) have been drawn up by four regional groups as part of efforts to develop a network of areas designed to improve the protection of the marine environment.

They range from a 2,200 square mile (5,698 sq km) site offshore in the south-west of UK waters which could be designated to protect seabed habitats, to around 100 acres (40.5 hectares) of coastal saltmarsh, saline reedbeds and mud flats in an estuary in the North Sea.

Benyon said that while the regional projects, made up of conservation organisations, fishing and marine industry representatives, leisure groups and other interested parties, had done excellent work, it was clear from the advice of an independent scientific advisory panel that there were gaps in the evidence supporting their recommendations.

"It is important that we get this right. It is vital that we have an adequate evidence base for every site if we are to create successful, well-managed marine conservation zones.

"An adequately robust evidence base will be essential when we come to implement management measures."

He said the Department for Environment, Food and Rural Affairs would be commissioning significant additional work, including an in-depth review of all the recommendations, and that extra resources would go to carry out seabed and habitat monitoring.

He said some zones could be designated fairly quickly where there was enough evidence for them but others would need more investigation.

The Wildlife Trusts, which last week raised concerns that the government was set to push ahead with designating just 23 of the proposed areas, welcomed the news that all 127 would be in the consultation.

But Joan Edwards, of the Wildlife Trusts, said: "Despite international evidence for the urgent need to protect our seas, the minister's statement will result in further unacceptable delay."

She said Defra appeared to be changing the level of evidence required after two years of the process, and that if more data were needed it could be gathered during consultation or after designation.

"We are disappointed that we now face a further delay of at least 12 months when more damage to marine habitats will continue to occur."

Kate Sugar, marine policy officer with the RSPB, said: "Two years ago, we were delighted that the importance of marine conservation - the Cinderella of UK wildlife protection - was finally recognised with the introduction of the UK Marine & Coastal Access Act.

"However, the latest position looks like Cinderella has returned from riches to rags - as far as English waters are concerned - as the government shows no ambition for providing a comprehensive network of marine protected sites to protect species as diverse as seahorses, corals, seabirds, whales and dolphins in a timely fashion."