North Norfolk MP Norman Lamb is calling for a half-hourly service on the Bittern Line as operators prepare to bid for the contract to run it.

Mr Lamb has written to the Transport Secretary Patrick McLoughlin pressing the case for rail improvements for north Norfolk.

He believes upgrades to the Norwich to Sheringham service over the past 20 years have boosted passenger numbers and had a 'significant beneficial impact' on the economy.

Now Mr Lamb says he wants a commitment to the long-term ambition of a half-hourly service between Sheringham and Norwich.

The East Anglia Rail Franchise, currently operated by Abellio Greater Anglia, will be opened to tender shortly, with three short-listed bidders having passed the pre-qualification stage.

The trio are Abellio East Anglia Limited (a joint venture between Abellio and Stagecoach); First East Anglia Limited; and National Express East Anglia Trains Limited.

The new operator is due to take over the franchise in October 2016.

The government is soon to publish the terms of what it expects the successful bidder for the contract to deliver in an Invitation To Tender document.

Mr Lamb said: 'It is vital that the government commits to significant investment in track improvements, and also sets the bar as high as possible for the new East Anglia Franchise.

A half-hourly service would require extra rolling stock and infrastructure investment north of North Walsham.

He added: 'It is absolutely paramount for this region that the next franchise delivers by continuing to invest.'