Traffic and economic forecasts prepared to justify the building of a new northern bypass across Ipswich do not stack up according to a new report prepared for campaigners fighting the proposals.

The Stop the Ipswich Northern Bypass group has commissioned the report from Bruce Bamber, a transport planning consultant who has worked on many road schemes across the country.

His 67-page report concludes that there is not enough information in the Ipswich Northern Route documents to make an informed judgement about the value of a new road.

Copies of this report and a petition are to be presented to Suffolk County Council's Endeavour House headquarters on Friday lunchtime after opponents of the new road have marched from Ipswich Cornhill to the council offices.

Meanwhile Central Suffolk and North Ipswich MP Dr Dan Poulter has written to county council leader Matthew Hicks expressing his concern that the consultation implies that building the road is a fait accompli - only the route of it is still up for discussion.

His letter says: "The evidence put forward by the county council to support a bypass is exceptionally weak and I remain entirely opposed to these proposals and shall continue to fight for the best interests of residents in my constituency."

He adds: "Please set aside these divisive and poorly evidenced proposals and let's work together on projects that genuinely benefit Suffolk."

Parish and town councils to the north of Ipswich have registered their opposition to a new road, although Ipswich Borough Council, town Labour MP Sandy Martin and Conservative parliamentary candidate Tom Hunt have all called for the inner route of the bypass to be built.

The consultation was promoted by Suffolk's public sector leaders - the county's six council leaders together with PCC Tim Passmore - although Mr Hicks, who is currently chair of the leaders' group, said they were not committed to anything further than discussing the contents of the consultation.

It is expected to take several months to analyse the results of the consultation - and no decision on whether the county council and other authorities should spend any more money on further development plans is expected for several months.