The last cigarette factory in Great Britain is to close. Imperial Tobacco is shutting its Nottingham plant, as well as its biggest Gauloises-producing factory in France, at Nantes. The two closures put nearly 1,000 jobs at risk.

Imperial employs 540 people in its factory and distribution centre in Nottingham, where it makes Lambert & Butler, Embassy, Regal, Superkings (known as John Player) and JPS (John Player Special).

The only remaining factory in the UK will be the one run by Japan Tobacco International in Northern Ireland.

Unite, Britain's largest union, accused Imperial of "social dumping" and shipping production to low-cost eastern Europe, and vowed to fight the proposed closures together with its sister French unions.

Imperial, which has 46 factories and 35,000 employees worldwide, employs 320 people at its Nantes plant and makes Gauloises, Gitanes and JPS. A further 120 jobs could be lost by the closure of its Bergerac research and development facility, although 80 new roles could also be created.

The company will retain smaller factories in Riom (Auvergne) and Corsica, but the French CGT union told Reuters the Nantes shutdown was incompatible with the forthcoming launch of "Gauloise Generation", a "100% Made in France" brand destined for the French market. The philosopher Jean-Paul Sartre smoked the original dark-tobacco Gauloises (Gauloises brunes, which have largely given way to a lighter version, Gauloises blondes), while singer Serge Gainsbourg favoured Gitanes – getting through up to five packs a day. Imperial said the restructuring forms part of plans to save £300m a year from September 2018.

Ten years ago, Imperial employed 1,000 people in Nottingham.

The tobacco company owns the business founded in Nottingham by John Player, who started out by selling pre-packed tobacco from his shop – until then smokers had to buy paper and tobacco separately and roll their own – and bought his first Nottingham factory in 1877, which produced pipe and chewing tobacco, as well as handmade cigarettes.

John Player later became one of the 13 companies that came together as Imperial.

Unite said Imperial had used increased EU regulations as a "cynical ploy" to shut the factories. The recent EU Tobacco Products Directive will stop the sale of packs of 10 cigarettes and "roll your own packs" below 30 grams. As a result of this legislation, Unite was expecting the closure of some manufacture lines and a knock-on effect on a small number of jobs. Unite's national officer, Rhys McCarthy, said: "This is shocking news that will have a devastating impact on not only hundreds of workers and their families, but also on the local community … It's another nail in the coffin for UK manufacturing and a loss of revenue for the exchequer."

The tobacco company blamed declining industry sales in Europe, due to tough economic conditions, increasing regulation, "excessive" duty increases and a growing black market trade. This has had knock-on effects on Nottingham and Nantes, which now use less than half their manufacturing capacity. Nottingham has capacity to make 36bn cigarettes a year but will only produce 17bn this year while Nantes, with a capacity to manufacture 21bn cigarettes, will only make 9bn. Production from both sites will shift to Germany and Poland. Imperial will still have nearly 1,200 people working in management, sales and marketing at its newly built head office in Bristol.

The company has told employees, works councils and trade unions about its plans. Chief executive Alison Cooper said: "These projects are an essential part of securing the sustainable future of the business. The prospect of job losses is always regrettable and we will be doing all we can to support employees and ensure that they are treated in a fair and responsible manner."

Cigarette sales have been falling by about 2-3% a year in volume terms in western Europe, but this has been offset to some degree by growth in eastern Europe and emerging markets. The global tobacco market is predicted to be stable, thanks to population growth. Imperial has identified Italy, Greece, Russia, Turkey and the US as growth markets, while the UK, with its 10 million smokers and where the company has a higher market share, is classed a "returns market".