There are six weeks left to find the £43m needed to save the Upper Orwell Crossings, Suffolk County Council’s cabinet has heard.

A new study into the costs of building the three new bridges across the Orwell in Ipswich concluded that the cost had gone up from nearly £97m to more than £139m – leaving a multi-million hole that needed to be filled if they could go ahead.

The government has pledged to pay £77m towards the project – but earlier this year Transport Secretary Chris Grayling made it clear during a visit to Ipswich that no more money would be made available for the project.

The county had budgeted to spend just over £19m on the project – and council leader Matthew Hicks told Tuesday’s cabinet meeting that it was not possible to find a further £43m from the council’s own capital reserves.

The county would spend the next six weeks looking for more support from various potential sources before putting the project on the agenda at December’s meeting.

Mr Hicks said: “We will talk to the Department of Transport, to the LEP (Local Enterprise Partnership), to Ipswich Borough Council and to (port owners)ABP in a bid to find this money.”

He added: “We are still committed to the Upper Orwell Crossings project, but we cannot go ahead with this if it means risking the financial stability of the authority as a whole.”

Costs had increased because of delays in starting work – and because the whole scheme proved to be more complex than was originally thought.

Mr Hicks was backed by fellow cabinet members, including Paul West who as cabinet member for Ipswich was trying to steer the project through the council.

He agreed that while the project was vital to regenerate Ipswich town centre, it was more vital that the council was able to function and provide other services.

Ipswich Labour councillor Mandy Gaylard said there were concerns among some local residents on both sides of the river about steps to ease the impact of the crossings.

But Mr Hicks said this was not a debate over the desirability of building the crossings – but over the proposal to discuss it again in December. He said it was just possible that it could be delayed until the first cabinet meeting in 2019.