Steve Bush of the Unite union, said it was "very disappointing news for Sunderland and the north-east" and reflected the "serious challenges facing the entire United Kingdom auto sector".
Nissan's Sunderland facility is the largest auto factory in the United Kingdom, employing more than 7,000 people.
Nissan said it took the decision on the X-Trail for business reasons, with continued uncertainty surrounding future United Kingdom.
Nissan was meeting representatives from Britain's biggest union, Unite, on Monday.
Ministers strongly denied any financial incentives were offered and Chancellor Philip Hammond said any costs arising from the assurances would be small enough to be covered within the Department for Business's existing spending limits.
The Government offered Nissan support of up to £80 million if the Japanese firm built new models at its United Kingdom plant, it has been revealed.
Mr O'Sullivan added there is "much more to do" to improve the government's web access and that Kainos has "strong credentials" to deliver, meaning their services are likely to be retained in the long term and will see further success.
Nissan's decision is another blow to the British vehicle industry, which reported a 46 per cent drop in investment a year ago as carmakers delayed decisions on upgrading machinery and factories amid mounting concern about the impact of a hard Brexit.
Business Secretary Greg Clark described Nissan's decision as "a blow to the sector and the region".
The leader of Sunderland City Council has called on the Government to do "everything in its power" to secure the future of the United Kingdom automotive industry, following the news that Nissan will be moving production of one of its new vehicles to Japan.
Less than two months before Britain's scheduled withdrawal date, the government doesn't have an approved agreement on the rules, conditions and terms that will replace the 45 years of frictionless trade that came with being an European Union member.
Production of diesel cars was down by 22% to 561,000 past year.
Colleague Julie Elliott said Brexit had played an "inevitable role" in the decision, adding "none of it is conducive to encouraging business investment in this country".
"The company has confirmed that no jobs will be lost".
"Therefore the company has chose to optimize its investments in Europe by consolidating X-Trail production in Kyushu".
Nissan's announcement comes a week after Jaguar Land Rover said it plans on cutting its global workforce by 4,500. The X-Trail production plans had been announced in the autumn of 2016.