Tiny rare snails which have colonised the dykes on a treacherous part of the A47 are likely to have four years to settle into a new home before a safety upgrade can begin.

Ecologists must make sure that the Little Whirlpool Ramshorn Snails – which are only found in Norfolk and Surrey – can survive and breed before their old habitat on the Acle Straight is moved.

About 800 of the invertebrates were relocated in the spring, but MPs were told it would take about four years to know if their move had been a success.

Under European rules, the dykes cannot be moved until the survival of the Little Whirlpool Ramshorn Snails is secured. They need to be monitored for a number of years to fully understand their survival and breeding patterns.

The four-year wait was revealed in a recently published letter between Highways England and Great Yarmouth MP Brandon Lewis earlier this year. In the letter, Mr Lewis told Highways England that it was ludicrous that the snails would lead to a four-year delay in moving the dykes, which he said caused tragic loss of life as cars leaving the road went straight into the ditches.

But Highways England said it had to abide by the law. A Highways England spokesman said: 'We are committed to upgrading the A47 in an environmentally responsible way.

'A number of protected species have their natural habitat around the Acle Straight and would need to be relocated successfully before any options for improvement can be considered.

'As part of the feasibility study, we have been working with partners including Natural England about the endangered Little Whirlpool Ramshorn Snails and carried out a pilot scheme of moving the species in the spring this year.

'It is still early stages as the snails will be monitored in their new location for a number of years to see whether this has been successful.'

Broadland MP Keith Simpson said people would be 'filled with exasperation' when they heard it was likely to take four years.

'I have every desire to try to maintain our environment and make certain it is not damaged.

'But it is almost as if what happens to snails and other beasties has a greater priority than the safety of the thousands of people who use the Acle Straight.

'We have had tragedies where people have come off the road and people have been drowned in the dykes.'

But he said that they should be 'grateful for small mercies' that the work to move the snails had started.

Great Yarmouth county councillor Mick Castle, part of the A47 Alliance, said it was 'almost unbelievable' that it could take so long.

'I am not against looking after the environment, but we have been waiting for so many years, and it seems like every time there is a glimmer of hope, there is something, this snail business seems to be the latest.'