A planned relief road would be a major economic boost to Shrewsbury, Shropshire Council has said.

It has published a revised business case for the North West Relief Road, which estimates the scheme would cost £215m.

Environmental campaigners held a protest before it was presented to a meeting at Shrewsbury’s Guildhall on Thursday.

Opposition parties announced earlier this month they would scrap the scheme if they take control of the authority after May’s local elections.

The draft Full Business Case updates a similar document published in November and sets out the possible benefits of the relief road.

The council said it would reduce congestion in the town and shorten the average journey time across northern Shrewsbury by 17 minutes.

It said this would also free up space on the roads for public transport and make it easier to walk and cycle.

The council’s business case estimated that for every £1 spent on the scheme, it would deliver economic benefits worth £3.88.

It said this ranked the transport scheme among those categorised as being “high value in the country”.

The leader of the Conservative-run authority, Lezley Picton, said the draft document made a “very strong case to the UK government for support and investment”.

She also said the £38m of government money already spent on the plans would be wasted if it did not go ahead.

But because local council elections are due to be held in May, there will be no chance for councillors to discuss the Full Business Case before the summer.

Opposition councillors attending the meeting on Thursday said they were furious the document was published 35 minutes before it was due to be held.

Some said they only discovered it had been published during the meeting.

Liberal Democrat, Labour and Green groups have all said they want the scheme scrapped, claiming it is too expensive and will not solve traffic problems.