Tiny snails holding up an Acle Straight upgrade must still be protected even if Britain no longer has to follow Brussels biodiversity rules post-Brexit, the transport secretary has said.

Planners face a four year wait for snails to settle before A47 Acle Straight work can even begin as ecologists must make sure the Little Whirlpool Ramshorn Snails – which are only found in a small number of places– can survive and breed before their old habitat on the Acle Straight is moved.

Speaking to the EDP and Norwich Evening News, Chris Grayling, who is in charge of the Department for Transport, said he took diversity in the natural world very seriously.

The prominent campaigner for Brexit said that even after we have left the EU he did not want to start 'adopting policies that say biodiversity is not important'.

Although he said there could be a 'bit of common sense' applied over relocating newts, which are classified as an endangered species, which often hold up housing developments.

He added: 'I don't think we can get into a world where we say the snail are rare and drive a road through them. We have got to be sensitive to these things.'

Highways England is about to start a consultation on upgrades to six other stretches, including creating three more sections of dual carriageway, on the A47.

Local MPs and former prime minister David Cameron criticised the road building body after it emerged it is unlikely to get diggers in the ground until 2019 or 2020.

Mr Grayling said that while they would try to speed things up, all major road schemes had planning periods attached to them.

'They don't happen quickly,' he added.

He said that while there were 'a lot of significant improvements on the way' on the A47, they were trying not to do too much in one go.

'If you have a series of improvements you want to keep the road flowing,' he said.

'The A47 needs long term improvement and there is a big block of things about to happen. There isn't a conscious delay. It does take time to get these things off the ground, but it is going as soon as we can.'