Highways England needs to spend £500m improving junctions on the A14 and A12 around Ipswich, including the notorious Copdock junction, to tackle rush-hour delays.

Suffolk County Council highways bosses told a meeting for borough councillors and members of the Ipswich Vision board that the government agency responsible for trunk roads needs to invest heavily on the existing major road network around the town.

The county backed up the calls of the Suffolk Chamber of Commerce which launched its “No More Delays on the A14” campaign two years ago.

Around Ipswich the most important – and expensive – problem is caused by the Copdock Mill interchange between the A14 and A12.

The county also wants to see improvements at Wherstead, Nacton, and Seven Hills junctions. The total cost of these projects could be half a billion pounds.

At Copdock Mill, where there are frequent rush-hour delays and regular accidents that can cause serious congestion, there have been regular calls for major work to ease the pressure on the junction.

One option could be to create a flyover allowing traffic between the A12 and the A14 to the east of Ipswich to avoid the roundabout and causing congestion there – vehicles heading into town along London Road would continue to use the existing roads.

The county is drawing up a list of projects that it is hoping to persuade Highway’s England to include in its next five-year investment programme from 2020-2025.

The county’s former cabinet member for transport Graham Newman was at the meeting and said it was important to keep up pressure on Highways England. He said: “There was not much that was new here, but the council must keep on making the case for investment in the roads.”

Stephen Britt from the Suffolk Chamber said: “An improved road and rail network is front and centre of our policy agenda, and is outlined in our No More A14 Delays in Suffolk campaign.

“As part of our campaign we will continue to highlight to Government the priorities for investment at the junctions around Ipswich, the emerging options and need for a northern relief road and the Upper Orwell crossings.”

The Chamber will be meeting MPs to press their case for road investment next month.