The A9 drops from 150m (492ft) to 20m (65ft) as it enters a valley at the Berriedale Braes.
Caithness Chamber of Commerce said it was taking too long starting construction work on the improvements and the problem was being ignored.
Transport Scotland said it was continuing to progress the design work.
The A9 provides a link to the far north mainland coast and the ferry services at Scrabster, Gills Bay and John O'Groats to Orkney.
Chamber chief executive Trudy Morris said: "For too long, the Scottish government has ignored the impact the Berriedale Braes has on those living and working in the North of Scotland and Orkney Isles."
She added: "While progress has been made in identifying a solution to this important issue, we are disappointed that the Scottish government is dragging its heels in moving towards a practical implementation of this.
"The project as it stands is effectively shovel-ready - all that remains is for Scottish government to commit the funding."
Last year, the Scottish Chambers of Commerce called for work to tackle the bend to be accelerated.
Government agency Transport Scotland said a significant step in the project should be taken later this year.
A spokeswoman said: "We are continuing to progress the design work for the Berriedale Braes improvement scheme following the publication of draft orders last year.
"We are currently working to resolve objections to the scheme and subject to completion of the statutory process we will look to publish made orders later this year."
Made orders mark the last stage in the development of a final design for a new road.

Peers backed a government bill paving the way for gay couples to marry. It is set to become law by the end of the week, with the first weddings in 2014.
Labour's Lord Alli said its passage meant "my life and many others will be better today than it was yesterday".
But Tory peer Lord Framlingham said the "ill-thought through" change had been "bulldozed" through Parliament.
Peers approved the principle of same-sex marriage last month, despite efforts by opponents to "wreck" the legislation.
MPs had earlier done the same, in the face of opposition from many Conservatives, the Church of England and other faith groups.
Supporters of the Marriage (Same Sex Couples) Bill wore pink carnations during Monday's proceedings in the Lords, during which a series of minor amendments - including one relating to pension benefits for same-sex couples - were proposed.
Government minister Lady Stowell said the bill "puts right something which is wrong" and had been improved by detailed scrutiny in the Upper House. "I can't claim to be a gay rights campaigner, but I am a firm believer in justice and fairness," she said.
But the Gay Marriage No Thanks group claimed it had been prevented from mounting an advertising campaign around Parliament after its truck was vandalised and its driver threatened.
After clearing the Lords, the bill will return to the Commons for a short debate on government amendments before the Commons begins its summer recess on Thursday. The bill must then receive Royal Assent before it becomes law.

The trio of Jack Carlin, Ryan Owens and Joe Truman repeated last weekend's win in Glasgow, again beating France into second place in Apeldoorn.
Emily Kay, who won the new-look omnium last week, finished second behind Kirsten Wild in the four-race event.
Chris Latham was second in the scratch race; Rachel James and Katy Marchant were fifth in the women's team sprint.
Britain did not qualify for the medal rides in the men's team pursuit, with senior academy riders Matt Wall, Ethan Hayter, Matt Bostock and Joe Holt recording the fifth fastest time.
Racing continues on Saturday with the men's sprint, women's keirin, women's 500m time trial and men's points race.
Find out how to get into cycling with our special guide.
The Scottish government has been accused of "dragging its heels" on proposed improvements to a challenging hairpin bend on the A9 in Caithness.
[NEXT_CONCEPT]
Same-sex marriage in England and Wales is a step closer to becoming law after the House of Lords approved the change.
[NEXT_CONCEPT]
Britain's men won team sprint gold on the opening day of the season's second Track World Cup in the Netherlands.