Only 70 per cent of people living in the centre of Spalding speak English as their first language.
The figure, revealed in data gathered in the 2011 census, compares to a national average of 92.3 per cent.
The town’s second most spoken language is Polish, with 13.31 per cent having it as their main language, compared to just one per cent of the country’s population. Portuguese is the next most used.
South Holland’s other major towns have a much lower proportion of native Polish speakers, with 89 per cent of Holbeach’s population speaking English as a main language and only 5.55 per cent speaking Polish.
In Long Sutton, Polish speakers make up 1.67 per cent of the total – 95 per cent have English as a main language and Sutton Bridge has 93 per cent with English and 3.27 per cent Polish.
In nearby Boston, only 57 per cent speak English, with Polish making up 15.39 per cent.