The warning follows publication a government bill to ban smoking in England in enclosed public places.

The Tobacco Workers Alliance (TWA) is concerned a cigarette factory and a filter-making plant could move abroad if the bill is passed.

Both companies involved, Imperial Tobacco and Acordis, said they had no plans to move production.

Brenda Warrington, chair of the TWA, said: "We don't see why our jobs should be exported abroad."

We feel that as long as tobacco is a legitimate product... we should have a sensible industrial base by which to provide that consumer product Brenda Warrington, Tobacco Workers' Alliance

Union officials have said Imperial's Horizon cigarette factory on Lenton Lane Industrial Estate in Nottingham and a site at Spondon, Derby, which produces filters, could be relocated to a country which is seen as less hostile towards the trade.

"Why should we have to go and work abroad just to maintain a reasonable living, that is not the way forward," Ms Warrington said.

"We should be able to accommodate and address everyone's needs in this matter."

The TWA is an alliance of unions in the tobacco industry.

Her claims were disputed by both firms who denied any plans for scaling down production in the UK.

Imperial Tobacco employs 900 people at its site in Lenton, the firm's only UK factory and the largest of its 32 plants worldwide.

Alex Parsons, spokesperson for Imperial Tobacco said: "Quite simply there are no plans to close the Nottingham factory.

"It's the largest factory we have in our global manufacturing portfolio.

"It's an integral part of the business and has benefited from over �27m investment in the last three years."

Paul Newing, spokesperson for Acordis which manufactures the material used in filters, said: "We don't feel in the short to medium term it will have a direct effect on employment.