The Suffolk Chamber of Commerce said the work could help boost the county's economy by more than £350m a year.
In 2013, the government announced a £1.5bn upgrade of the Cambridgeshire section of the road, ruling out initial plans for a toll.
Suffolk Coastal MP Therese Coffey said the road was currently "not delivering" a "quick and efficient" route.
"Businesses rely on goods coming into the port of Felixstowe being transported in a quick and efficient manner, something the road is not currently delivering on," said the Conservative MP.
The twelve sites identified stretch from Exning to Felixstowe, and include the Copdock Interchange.
The areas named in a document called  No More A14 Delays also includes junctions in Exning, Bury St Edmunds, Ipswich and the Orwell Bridge.
It calls for various improvements, such as extra capacity at junctions, better links with other roads, improved parking facilities for lorry drivers, extra lanes and reduced speed limits on the Orwell Bridge.
The document states: "An end to congestion on the A14 in Suffolk could generate up to £362m of extra gross value added (GVA) per year, saving the A14 user an average 13 minutes per day in travel time, and creating an additional 7,000 jobs."
Jo Churchill, Conservative MP for Bury St Edmunds, said the route was crucial as "nearly 30% of all the UK's container trade passes through Needham Market, Stowmarket and Bury St Edmunds along the A14".
Nick Burfield, policy director at Suffolk Chamber, said: "The chamber and our partners are very concerned that, following the success of the 'No Toll Tax on Suffolk' campaign and the proposed Cambridge to Huntingdon improvements, the government may now regard the A14 as 'done'.
"This is far from the case."
A Department for Transport spokeswoman said: "The government is committed to regularly reviewing the needs of England's strategic road network.
"We will be outlining plans for developing the next Road Investment Strategy later in the year, and we want every community affected by heavy traffic to have their chance to get involved."

Former Humberside Police Det Ch Supt Colin Andrews allegedly carried out the rape in a hotel room in December 2003.
The 58-year-old pleads not guilty to seven charges including rape, stalking and harassment.
Manchester Crown Court heard he denied putting his hand over the mouth of a woman while he raped her.
Cross-examining Mr Andrews, prosecutor Owen Edwards said to him: "You wanted sex whether she wanted it or not."
The father-of-one replied: "No. that's not me."
Mr Edwards then asked: "You got on top of her didn't you?"
"No, there was no sex at all, of that I am certain. No sex that night, absolute fact," replied Mr Andrews.
Mr Edwards said: "When she screamed you put your hand on her mouth and had sex with her. Is that rape?"
"I would say so but that is not what happened. I did not rape her, that did not happen," replied Mr Andrews.
"I have never put my hand on any female's mouth ever during sex.
"Whatever she's describing, I never had sex with her. I never attempted to have sex with her. I have never forced myself on anyone, I would never do that."
Since the start of the trial, the court has heard Mr Andrews described as "controlling, manipulative and bullying".
The jury has been told the defendant held his hand over the woman's mouth while he raped her.
They also heard accusations of him pursuing a campaign of stalking and harassment against another woman in the summer of 2013, during which he sent thousands of text messages and emails.
Giving evidence in his defence on Thursday, the former detective broke down in court as he told the jury about his early police career.
The court also heard how he was the force's most decorated officer and was described as "loyal and dedicated" by a former colleague.
Mr Andrews also denies two counts of common assault, assault occasioning actual bodily harm and witness intimidation.
The trial continues.
Campaigners calling for improvements to the A14 have listed 12 sites they say are in need of improvement.
[NEXT_CONCEPT]
A senior detective accused of raping a woman after a Christmas party has said in court he "never forced myself on anyone".